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My Headlights Stay Up After Adding Headlight Relays


juddev

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That is what I thought when I first read the post, but if wired in conventional manner, power in on terminal #30, is routed to #87 when energized and #87a when not. Since the power fed to #30 is always "hot", when the relay is inactive, #87a is now "hot", energizing whatever is connected to it? I wonder if maybe wired backwards, with power in on #87 and out on #30? The power would then be prevented from flowing out #30 or #87a? I'm too fuddled to make a better guess, but I just don't see how it would work unless the signal to the HDM is relocated. I just can't get a handle on how that would work?

I think the OP solved his issue by leaving a the fog lights engaged creating an alternate path the HDM likes.

Edit: I do like the idea of repurposing terminals, or replacing, but I think there will be splices somewhere anyway and the factory apparently did so for no apparent reason. Done properly, they shoudl cause no issues.

Edited by 2seater (see edit history)
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Guest Mc_Reatta

Correct wws944, both new relays need to be single pole double throw (SPDT) as stated. These are the same relays as use in probably 30 other locations in the car already. Do not use relays supplied by some headlight specific vendors if they are double pole single throw (DPST) as these will make you life miserable.

The important concept of the wiring is the new wire to the low beam headlamps needs to be connected to pin 30 which allows them to be switched between the NC pin 87a and, when relay is enabled, pin 87 (NO)

Fused battery power is connected to pin 87, and the lights on signal (I suggest from the tan wire that is originally connected to the low beam filaments) is connected to both pin 87a (NC) and either of the coil pins 85 or 86. The unused coil pin (85 or 86) is then connected to ground.

The yellow wire to the HDM is connected to the tan signal wire already via an existing splice (S255 or S117 depending on year).

Thus when lights are off the headlight filaments are connected via the NC contact to the unenergized signal wire (the old tan wire to the headlight) which allows the HDM to drain to ground thru them just like stock, so it will close the doors if bulbs are good, or keep them open if bulbs are burned out. The battery voltage on the NO pin has nowhere to go.

When the headlights are turned on, the relay is energized via the signal wire, which removes the connection of the bulbs from that same wire (NC contact), and connects them to the battery directly thru the NO contact. Thus clean power goes to the lights, the NC contact hangs in the air, but the yellow wire (which is spliced into the signal wire) sees 12 volts from that existing wiring and raises the doors.

High beam side is the same, just substitute the light green wire for the high beams with all references to the low beam tan wire.

Don't forget to provide a good ground to the common ground pin of each bulb especially if you remove the existing connector from the bulbs to tap into those signal wires.

All existing functions are maintained, and no modifications to existing wiring needs to be done.

I added the conventional pin numbers to the diagram for clarity.

post-55241-143142153214_thumb.gif

Edited by Mc_Reatta (see edit history)
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In my best Homer Simpson fashion, DOH! MC, I knew you knew what you were talking about and had posted the diagram earlier, but I skipped right over it, while pursuing the elusive yellow wire. Blind to what you were trying to communicate so to speak :( It makes perfect sense when my eyes are open to all input. The most elegant solution is also the simplest.

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I'm not certain I should post this quite yet as my good voltmeter decided to lose connection to the 9v battery making the display disappear, so I cannot confirm my conjecture, but perhaps there is some insight into the new relay system behavior. I do not have a good headlight switch to install as of yet but, I jumpered power momentarily to the yellow wire which should be the headlight switch output. The headlights immediately popped up and turned on, but, removing power from the headlight switch output had no effect, in other words, the lights stayed up and illuminated. Removing the relay that was activated caused the headlights to go out but the headlight doors remained open. Reinstalling the relay caused the doors to close, so it does see the original yellow wire connection to close the doors. My suspicion is there is power coming in on activation wire (original hi or low beam wire) that is enough to hold the relay engaged, although not enough to actually cause it to pull in? The only source I can think of is the original Hi-Lo relay in the console, but it is powered by the yellow wire from the headlight switch or something from the door module? I did go over my harness several times and also tried different relays.

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Guest Mc_Reatta

Not sure you're saying there is a bad headlight switch currently in the car, or there is no headlight switch in the car.

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Sorry for the lack of clarity. I have no switch in the car. The switch went bad, not certain of the reason, but that prompted the much delayed headlight power upgrade. There are just two bare plugs in the dash, and I applied power to the yellow wire that runs down to the hi-lo relay in the console which also contains the splice for the wire to the door module.

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Guest Mc_Reatta

I hope you haven't uncovered a quirk of the headlight module that couldn't be foreseen. I don't know why the relay wouldn't drop out as soon as power was removed.

Think I will wait until you can get some voltage readings again to see if there is something strange in the works or not.

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Yes, I will see what's what. I have an old analog 15 volt meter on the wall that hangs above the workbench just for quick checks. It may be actually easier to connect that so I can see in real time.

Dave, I call if I can arrange something, maybe Fri. morning?

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I just connected the voltmeter to the activation wire for low beam relay and it acts as before. Apply 12v to the output wire for the headlight switch B7, the meter shows full battery voltage and everything activates. Disconnect power from B7 and the meter voltage drops to about 5.5v, apparently enough to keep the relay pulled in. If I pull the hi-lo relay in the console, the lights go out and meter voltage drops to zero, but the lights stay open. If I replace the hi-lo relay, the headlights close. I repeated the test with new relays in both positions and the results are the same. It just dawned on me to check for voltage on the yellow wire, like a backfeed from the module?

EDIT: Yep, there is a little over 5v present on the yellow wire at the headlight switch, which I imagine is the drain voltage from the headlight module. Maybe there is a reason the factory added the single on-off relay, aside from simplicity?

Edited by 2seater (see edit history)
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Guest Mc_Reatta

The worm turns. Believe this is the result of a logic circuit "high" that could be from the BCM or HCM. Would need to disconnect one from the yellow wire and see if it stays or goes away, but other than knowing the source, it doesn't really matter. It's there and needs to be dealt with.

The resistance of the relay coil (~50 ohms) is too great to bring this down to a "low" value as the headlight filaments (~2 ohms) do.

I'll have to give some thought to how best to correct this problem, but think the ability of the HDM to sense a burned out headlamp may be sacrificed in the bargain.

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I have been following this thread with great interest as I just converted my '89 Reatta from Halogen to 35w HID low, halogen high beams. As the original Halogen low beams were also 35 watt, I did not worry about overloading the headlight switch, BUT I still fully intend to install relays to (1) bypass the headlight switch as the current carrier to the headlights for both low and high beams, (2) make low and high beams both active whenever high beams are activated (HID manufacturer specifically stated this was acceptable behavior with the lights and housing) & (3) to keep the LOW beam active for a fixed time, (approx 1 minute) after the headlight switch is moved to the off position (ie manually on, Twilight Sentinel-like off). I have the circuit all designed but have been holding off as this thread progressed.

FYI, the headlight doors worked as expected after the HID initial conversion (ie no bypass relays, just factory wiring). The HID conversion was a plug and play install, connecting directly to the factory connector and WHAT a difference in illumination. My bypass/twilight setup, ALSO will be plug and play BETWEEN the factory wiring and the HID wiring. At any time I could pull all of this out and simply plug in my old Halogen bulbs.

All this discussion of the headlight door behavior after adding bypass relays had me very curious if it was generic or specific to juddev's Reatta, so I investigated the behavior of the headlight/headlight doors/HDM/BCM circuits on my '89 Reatta (late 88 build). I have NOT modified the factory wiring or headlight connector in ANY way. I did all voltage measurements AT the factory headlight connector low beam connection point.

1st, I unplugged BOTH headlights (ie the new HID/Halogen) and switched on the headlights. Doors went up. Switched off the headlights (low beam) and as expected doors remained up. Then I plugged in just ONE HID unit and the doors immediately retracted. Then I repeated the headlight ON/headlight OFF test, with just the one HID/Halogen plugged in (tried both sides separately) and with just ONE side being connected, the doors went down immediately when the headlight switch is moved to off. So that pretty well says that the door operation was NEVER intended to be a headlight OUT monitor as it would require BOTH headlights to be out in order to not close the doors as expected when the headlights are switch OFF. It appears that GM was just using the headlight filament as a low resistance path to ground for the HDM (ie effectively a pull down resistor).

2nd, I disconnected BOTH HID/Halogen units then temporarily wired an automotive 40amp SPDT relay between the low beam connection of the factory headlight connector and ground. I then switched on the headlights, doors went up, then switch the headlights off and doors went down immediately. FYI, I measured the resistance in the coil winding of the relay I was using and it measured 87 ohms (spec that I have found on these shows 75-90 ohm nominal). So the fact that with ONLY one relay connecting the low beam power connection on the factory wiring to ground via the coil winding is sufficient to close the doors IMMEDIATELY on switching the headlights off would seem to indicate that the higher resistance of the relay coil IS NOT sufficient to make the HDM think the headlights are still ON.

3) As 2seater had reported that he was measuring around 5volts at the hot side of relay coil AFTER switching off the headlights and the relay contact retained, I was curious if I would find the same thing. I connected my digital voltmeter in ohms mode across the Normally OPEN relay connections. In initial power off state, infinite resistance (ie no contact). Then I switched on the headlights, and the resistance dropped to around 1 ohm or so and the doors went up. Then I switched off the headlights, the doors immediately retracted, BUT the Normally OPEN relay contacts held (ie relay is still holding). I then measure the voltage and sure enough, just as 2seater measured, about 5.2 volts. BUT THEN, I heard a soft click and the relay dropped out and the voltage on the relay coil dropped to a few mV. I repeated the test again, same results, with the relay dropping out (ie voltage dropping to a few mV) 5-7 seconds AFTER the headlight switch was moved to off. The soft click IS coming from the relay box under the hood BTW.

I did NOT test to see how the voltage on the low beam connection behaved with a standard Halogen bulb installed. It may WELL immediately drop out due to the low resistance of the Halogen filament, BUT even with the higher resistance of the relay coil, WHOEVER is supplying that 5.2v after the headlight switch is moved to off, does drop out, at least on my '89, after a few seconds.

I have no idea why juddev's relay setup is tricking the HDM into believing that the headlights are still powered up (ie keeping doors open), but from my testing, using a relay (wired in as Mc_Reatta posted), should NOT affect the headlight door operation as the relay coil resistance provides a sufficiently low resistance to ground to lower the doors immediately even if the voltage at the low beam connection remains around 5V for a few more seconds. Of course, this delay in releasing the relay DOES mean that the headlights themselves WILL remain ON for a few seconds AFTER the doors retract.

So, I think I am going to move forward with the next phase in my headlight upgrade project. One additional thing I learned from this testing was that the low beam voltage with the HID unit connected (engine off) measured 9.6v, which explains WHY my original Halogen bulbs were so pathetic and ALL the more reason to get the high current away from the headlight switch itself. Once I have completed the next phase I will post results and be happy to share the design with the forum.

David T.

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Thanks for the detailed investigation. Since I do not have a headlight switch installed, I cannot see any means for the BCM to cause any power feed to the activation circuit as that appears to be isolated to a connection through the switch. I did leave the lights in the "on" position for a couple of minutes with no power on the headlight wire from the switch, so, if there is a delay, it is longer than I am comfortable with. I do not know if there are wiring differences between the years mentioned, but I think some had a separate headlight up-down switch on the console which the '90 lacks. Not sure if that is germaine? Five volts seems to be a common sensor voltage, although maybe just a coincidence or the product of the available voltage and resistance? It doesn't really matter I suppose, just how to deal with it. I would not mind losing any sort of headlight out warning, and it looks like it may have been used as an explanation of the headlight door operation? It would not take a lot of rewiring to do the headlights the other possible way, with an enable relay and a hi-lo selector, so that option is still available.

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Guest Mc_Reatta

DavidT, Thank you so very much for researching this circuit so thoroughly for us!

It is what I hoped to learn after the weather cooled and some of the mosquitoes died off this fall.

So the HDM is not as smart as I thought it might be and can only tell if both headlights are burned out, not just one.

In this case I think trying to retain that capability is not worth the effort. I think most of us would realize if we didn't have any headlights on just by looking at the road.

The new dilemma is how to come up with a way to create a pull down resistance for the HDM while not drawing too many amps thru the headlight switch which is one of the main reasons to create a harness in the first place.

I thinking about two possibilities. The preferred one I would try first is to add a resistor in line with the relay coil. Not sure of the minimum voltage needed to cause the relay to activate, but we know a voltage of 5 volts is sufficient to keep the relay energized. I would start by adding a resistor of around the same value as the relay coil (~80 ohms) which would drop the voltage the coil sees when energized by approximately half or about 6 to 7 volts. This might need to be tweaked depending on the specific coil used and the voltage supplied thru all the circuitry before the signal gets to the headlights. Rat shack has 5 packs of 47, 68, and 100 ohm resistors cheap and in stock. Can be either 1/4 or 1/2 watt. I'd try a 68 ohm first and see what happens. If relay doesn't make, reduce the resistance. If relay makes but doesn't drop out when switched off, increase to 100 ohm one. I don't have access to test equipment any more that I could test this out first, so trial and error method will have to do.

Likewise, the retained voltage of the HDM would be cut in half when de-energized which would drop it from 5 volts to 2.5 volts which should not be sufficient to keep the coil energized enough to hold, so the relay should drop out when headlights are switched off and then allow the HDM to drain thru the wire added to the normally closed relay contact thru the headlights to ground. This added resistor is a pull down resistor for the coil.

This is the preferred method as it will further drop the current thru the headlight switch from ~ 150 ma to around 85 ma which is a great improvement from what the stock circuit sees of ~ 8.5 amps on 55 watt high beams.

New diagram:

post-55241-143142166874_thumb.gif

Edited by Mc_Reatta (see edit history)
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I really question if it is necessary to worry about the relay holding in for a few seconds that I observed. In my testing, the doors IMMEDIATELY closed when the headlight switch was moved to the park/off position. On thing we SHOULD do is put a diode across the relay coil to shunt the reverse voltage that happens as the magnetic field of the coil collapses when the power is finally shut off. Just attach the diode (1N4148 recommended) across the coil relay with the anode attached to ground and the cathode to + connection on the relay. This is just common circuit design practice when mixing relays with solid state electronics.

If others also find that the HDM drops its sense voltage after a few seconds, then I don't see the harm of allowing the headlights to remain powered up (ie relay holding) during that period even though the doors have retracted. We need to get more data points on this behavior before assuming it is generic to the Reatta HDM module. We also need to verify if there are any differences between the 88/89 and the 90/91 models behavior.

Adding in additional resistance in the coil circuit will lower the overall current through the headlight switch, though once we are in the lower milliamp range, additional reductions won't lengthen the life of the headlight switch perceptibly. Typically, dropping the coil voltage to 4 volts or so will unlatch the relay, but as each coil winding has some variation, the exact voltage will vary as well. These relays typically won't pull in until the voltage is around 9 volts or so but again it can vary +/- somewhat.

With 9v as the target coil pull-in voltage desired, we need roughly 110ma through the coil (87 ohms X .11amps = 9.7v) Assuming 12V nominal and 87 ohm in the coil, the MOST resistance we can add into the coil circuit is 23 ohms giving us a total resistance of 110 ohms (12V / 110 ohms = 109ma). With that amount of added resistance, at the 5.2v HDM sense voltage, the voltage drop across just the coil will be 4.1 volts (5.2v / 110 ohms =47ma therefore 87 ohms coil X .047 = 4.09v), which is close to it minimum holding voltage, so it may OR may not release the relay. So the amount of resistance needed to ensure that the coil releases at the 5.2 HDM sense voltage will likely PRECLUDE the relay pulling in at under the nominal 12V across the coil and added resistor. This does not look like a workable solution.

In measuring the voltage at the low beam connection while running 35W HID bulbs, I measured 9.8 volts which indicates that on MY Reatta, the resistance in the headlight switch and factory wiring is approx .722 ohms. While this is a small amount, at 3.6amps (ie 35w beams) that causes a 2.6v drop between the battery 12.4 volts and the measured 9.8 at the low beam connection. Now if you remove the headlights themselves (ie powered by relay directly from battery) and replace that with the 87 ohm coil resistance & the 23 ohm additional resistance, the drop in the headlight switch and wiring is an insignificant .08 volts. Even without the added resistance (ie JUST the coil resistance), the drop is still an insignificant .1volts. So the inherent resistance in the headlight switch and factory wiring would NOT impact that values I calculated above to any operationally significant amount.

Which brings me back to the fact that IF all Reatta HDM modules behave as mine (ie drops the 5.2v sense voltage after a 5-10 seconds) then it seems acceptable to just allow the headlights to remain illuminated for that time WITH the doors retracted.

David T.

Edited by drtidmore (see edit history)
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Guest Mc_Reatta

Good analysis.

Same HDM was used in all years but whether they all act the same remains to be seen. How long the 5 v will be present before it bleeds off may vary significantly in 20 year old modules.

Agree use of diode across coil is good practice.

I generally use a higher than 12 volts for calculations allowing for operating boost from alternator.

Think some experimentation will be needed to get the harness to work exactly as desired given all the variables involved, but this design should be a good starting point to achieve it.

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I meant to get back to this yesterday, but I will post my results now. I activated the headlights as stated before and left them activated for a full five minutes with no power to the headlight switch wire. The approx. 5 volt signal did not decay perceptably during that time, so everything stayed energized.

When this issue was discussed initially, way back in the beginning, there was mention of relocating the yellow signal wire, between the headlight switch and the HDM module, so the module could see the bulb filament. I know there are two inputs to the HDM and the surmise was ths was for quad bulb setups. Originally my plan was to operate the relays as an enable relay and hi-lo selector. The yellow wire would be cut before the splice where it splits to the module, the feed portion of the wire direct from the switch would activate the enable relay. The end toward the HDM would be connected to the power input to the hi-low relay, which mimics the factory wiring. In this case, with discrete hi and lo relays, the two feeds to the HDM would be individually connected to the output of the relays, the feed wire from the switch would be terminated. I do not know if this will cause the headlight doors to activate momentarily when switching beams? I of course do not know if there would be any crosstalk inside the HDM to cause power out to the unlit filament? As it stands, it would be fairly easy for me to try it since I know where the splice is and my relays are about 6" away, but, I would have to actually cut the wire to prevent backfeed as we are getting now. I am certainly no expert, and could certainly use input as to the feasibility before I do so.

Edit: I admit much of the calculation was beyond my immediate comprehension, but I agree the system voltage could be somewhat variable, probably ranging from a somewhat hi alternator voltage output to running home with alternator failure and only battery power to get there. I don't know at what level the ignition system will fail to function, but I would like the keep the option of headlights in a pinch, as remote as that chance may be.

Edited by 2seater (see edit history)
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I have gone back thru this entire thread trying to ascertain exactly HOW 2seater has wired in his relays and I am STILL not certain. There is certainly something different happening between how 2seater has the relays wired and how I am testing in my 89. Again, ALL my factory wiring is intact, NO mods. I am testing AT the low beam headlight connection with NOTHING connected to the high beam connection. Either of our experiences may be a specific-to-car situation rather than a generic model behavior. We need more people from both era Reattas to do some quick testing similar to what I did and previously posted. Data is key to understanding the actual generic behavior and if there are differences.

My feeling on relieving the headlight switch of ALL high current carrying requirements is ONLY part of the problem. As 2seater has pointed out the factory wiring harness is at best marginal. I also DON'T want to modify ANY of the factory wiring PERIOD. My approach is to solve this issue working FROM the factory headlight connector as it actually gives us the everything we need and from my testing keeps the rest of the electronics pretty happy as well. I am NOT going into the wiring harness at ANY point to make mods. I will be using the voltages presented at the factory headlight connector to control separate relays for low and high beam (each powered directly from fused battery connection).

I did review the 89 FSM for the headlight door switch on the console and all they are doing is switching 12v directly to the HDM "Headlight doors open input". 12v is also feed via a blocking diode from the headlight switch to the HDM "Headlight doors open input", which provides the normal signal to open the doors. So the separate door open switch on the 88/89 models adds nothing really pertinent to what we are chasing.

As for using higher than 12v for nominal voltages, I agree that 12v will more likely be 13.5 or so when the alternator is running. I used 12v as even without the alternator under typical engine running conditions, we can still pretty much rely on having 12V, at least until the battery begins to discharge. What I was trying to point out with all my calculations is that adding resistance to the coil circuit is going to be on thin margins due to the pull in and release hysteresis (9v pull in, 4v drop out) on these automotive heavy current relays.

David T

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Yes, thanks to Dave I have completely operational headlight switch, so at least I do not have to jumper B+ to the headlight activation wire. It operates exactly the same as previously described. I use relay sockets equipped with approx. 12" pigtails for connections. The relays are wired exactly per Mc's diagram. 86 and 87a are tied together and connect to the original headlight wire for activation. 85 is ground with no splice to the left fender support using an original bolt hole, paint removed and a star washer under the ring terminal. Also is ground for the left headlight. All connections are bare crimp rings or butt connectors, soldered after crimping and heat shrink applied. 87 routed to 25A breaker connected to the stud inside the red plastic box on the right fender near battery. 30 is power out to the headlight. I have verified every connection I have with an VOM and tried all combinations to eliminate the possibilty of accidental cross connections. I applied power to the #30 terminal in both relay sockets to be certain the lights operate properly for hi and low beam. Now that I have a headlight switch, I should verify hi-low operation from the dimmer switch and try shutting them off on hi, although should default back to lo beam with power removed? I will also try this with fog lights applied as done by the OP.

Not intending to be a wise guy, but the factory didn't seem to have an issue with splices within the wiring harnesses. Not that I want to do so, but my simple logic tells me that the factory connected the wire to the HDM after the on-off switch to the lights, the headlight switch in early '90 production and after the enable relay that was added in later production.

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MEA CULPA:

I was going to delete the above post and repost it but if anyone has already read it I need to restate what I thought I knew and see about adding a big red faced emoticom. I do not know what this means but, after operating the dimmer switch back and forth, it appears the initial default on my system is to hi beam. In any case, if I switch to low beam, and then turn the lights off, the lights go off and the doors close. If I reengage the headlight switch, the lights open and turn on, but are on hi beam again. What makes this even more confusing, is they operate differently if I reverse the relay positions. I don't think I will detail the differences, but I suspect it is because of two different relays. One is a PEI brand and the only reason I used it is because it has a mounting tab that I can hang both relays from. The relay sockets are designed to be ganged together so both are supported from a single fastener. The other relay is a Siemens brand, which I have many of. The only difference I can see on the diagram on the case is the Siemens has a + and - on the 85 and 86 connection, and it will not work if reversed, so I imagine it contains a diode? I did not try reversing them on the PEI. I truly apologize for running everyone in circles. Please don't waste your time until I reverify my wiring. Maybe it is the mixed relays, something goofy about the default from the original Hi-Lo relay in the console or something else. Three things are now consistant, one is the headlights always turn on and open, are on hi beam when they do, and will only turn off and close if in lo-beam postion.

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The following was posted between your two posts. Sounds like you wired the high beam connection to what you thought was your low beam filament.

2seater, Glad to hear that you have a new headlight switch. I replaced mine just the other day. The original one was functional but I had to punch the off button several times to get it to power down the park lights. The replacement switch looks virtually NIB and works wonderful. Actually I don't think the original switch EVER worked as smoothly was the one I purchased from a fellow forum member that was cleaning out his spares after selling his '89.

So, from your post I take it that the headlight doors still do NOT retract NOR do the headlights themselves power down when you turn off the headlights with your newly installed switch (that was what you reported previously) with the relay installed for each headlight.

One question, did the headlight doors and headlights work properly before you did the mod?

As I have stated, I have already converted my Halogens over to HID which in effect eliminated the headlight filament path to ground for the low beam, YET, my doors and headlights work EXACTLY as they did with the original Halogens. The conversion to HID did NOT involve ANY wiring mods. The HID harness simply plugged directly into the original factory sockets (ie drawing power through the headlight switch). As I also detailed, I removed BOTH HID units (ie NO headlights) and put a 40 amp automotive relay coil between the low beam headlight connector and ground and the doors worked perfectly, but the relay did HOLD for 5-10 seconds after the doors retracted once the headlight switch was moved to OFF.

My plan is to use two relays per headlight, each wired as per Mc_Reattas post above except 87a will be unused since testing on my Reatta has shown it not necessary. The fact that the 5.2v sense voltage keeps the relay engaged for 5-10 seconds after door retraction does NOT bother me and I don't have a low beam filament with the HID bulbs anyway (the low beam wiring actually now goes directly to a digital HID power module). I seriously doubt that the HID power module has as low a resistance as the Halogen bulb and as I have stated but my Reatta HDM does NOT seem to mind the change over to HID or a relay coil in place of the original Halogen bulb.

David T.

Edited by drtidmore (see edit history)
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Guest Mc_Reatta

Sounds like progress has been made.

DavidT, have you measured the resistance of the input of the low beam power supply for your HID lights?

2seater, does sound like the Simmons relay has a built in diode, and the differences between the two are why one shuts off and the other doesn't.

The BCM should default to low beam on initial turn on, but might hold hi beam on if the lights are turned off but the BCM was not powered down. Not sure of that, but possible given how the hi beam is switched on via the BCM, and that the relay is always powered on. Easy enough to test out.

Either way, sounds like you just need to reverse the tan and light green signal wires from your stock headlights to your two new relays to get things working right.

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Thanks to you both for not yelling at me, but I would deserve some. I did reinvestigate my wiring harness and I did indeed make a mistake although not the cause of the weird functioning. I did reverse the connections to the headlights themselves at the relay sockets. The relay activated by the low beam (tan) wire was outputted to the high beam filaments, so apparently I traced over and over making the same error. I guess a nights sleep and fresh look uncovered that issue. Before I discovered that issue, I went to the interior relay for hi-lo thinking perhaps the BCM had somehow gone south and was pulling in the relay upon initial activation. Probing the back of the hi-lo relay connections in the relay center proved that all was working properly, default was indeed the lo beam (tan) wire. I had previously tested the relay itself for proper operation. I next pulled two of the factory Hella brand relays from the horn and a/c positions and installed them. The headlights now function as expected but there is a slight difference depending on the beam position @ shutoff. If in the default low beam position, the lights retract but do not shutoff, just as described by David T. After 5-7 seconds, there is a soft click from the relay and they turn off. If in the hi beam postion, the lights go out immediately and retract normally. My basic thinking on that would be the power to the lights drops out when the O.E. relay in the console defaults back to idle. I then tried two matching Siemens relays and the lights again acted as previously described or worse. Again, depending on beam, the lights may go out but the lights stayed open. Clearly, this setup does not like whatever is inside the Siemens relays. The symbol for the 85-86 side is marked + and -, which is not on any of other three brands of relays I have. The little diagram shows a straight line with a diode symbol between the two terminals with a switch symbol (rect. box w/diagonal line?) connected to across the ends of the diode. The diode symbol is very small and does not have much contrast to the case (black on black), so I did not notice it. I next switched them out for a Bosch and the PEI relays and the lights work just as with the Hellas. In the default lo beam position, they immediately retract and lights out after 5-7 seconds. Perfect operation as far as I am concerned. I feel somewhat better that it was an incompatible parts issue rather that an error in wiring (aside from the reversed hi-lo). I even switched relays around but there was always one of the Siemens in the mix, with changes in the headlight operation, but apparently never hit on the proper combination. Upon reflection, that should have been a clue.

This headlight system does function just as originally described and I truly appreciate you sticking with me. Now I just need to switch the connectors in the relay sockets, which should be a piece of cake after all this. Whoopee!

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Guest Mc_Reatta

Since only folks who have never committed a blunder are allowed to yell you're safe.

Sharing of experiences, information, and knowledge is how we make advances here on the forum. Since we don't have much information concerning all the Delco black boxes and software, assumptions must be made and performance checked and adjustments made. Mistakes will be made and are part of the process unfortunately. Edison made over 1000 attempts before he got a working light bulb, so you've got a ways to go.

Those Simmons relays should probably be reserved for a different project since they seem to have a higher resistance than a standard relay which is not desirable in this circuit.

I am going to be mulling over the fact that the relay turns off quicker on the hi beam side then the lo beam side. First thought is it's a slight difference in the two relays, but you said swapping the relays side to side doesn't make a difference. The next obvious thought is the different contacts used in the high / low beam relay and the green and tan signal wire. Might try swapping the hi/lo beam relay with another relay and see if that makes a difference. I'd check the voltage readings on the hot side of each of the new relays to see if there is a difference between them when each relay is activated. Maybe dirty contacts or some frayed wires in the hi/lo beam relay and signal wires are causing this.

Glad you have got this working OK now. That new headlight switch and the rest of the headlight circuitry thanks you, and your headlights should be brighter too!

Edited by Mc_Reatta (see edit history)
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Really GLAD to hear that 2seater has replicated the sequence of events that I see on my Reatta using ONLY a relay coil for the HDM path to ground. As I have said, the headlights remaining on for 5-10 seconds AFTER the doors retract does not represent a problem in my book. Glad to hear that he found no issues with powering down from high beam as I had not yet tested that scenario. As my low beams are now HID, connecting the HDM directly to the HID power supply on power down (ie 87a tied to 86 on relay) vs just leaving it connected ONLY through the relay coil seems a mute point, so I am just going to forgo attaching the 87a connection on the relays to anything (ie I will be using the relays as SPST).

It certainly appears that we have a working solution to move ALL the high current away from the BOTH the headlight switch AND the factory wiring harness.

FYI, I recently replaced BOTH my license plate lens/sockets as the heat from the 194 incandescent bulbs had baked both of them to failure. To avoid a repeat, I installed Sylvania high output 6000K white 194 LED bulbs (Autozone) and WOW! The difference in illumination is night and day and NO heat!

Now to tackle the 12, 2057 incandescent bulbs in the taillight. Those things consume 2amps in taillight mode (166ma each), and a whopping 16amps in stoplight mode (6 bulbs X 2.66amps each). At least all these bulbs are powered through relays rather than the headlight switch. I am researching LED options, but wondered if anyone on this thread has already found really good LED equivalents? I know that the Turn/Hazard module monitors aggregate current being drawn by the turn filaments and provides a visual clue to the driver (fast flashing IPC turn indicator) if even a SINGLE turn/stop filament is bad. I can install a power resistor in the circuit to fool the module, but that won't reduce the current being pulled through the factory wiring. There does NOT seem to be any monitoring for taillight filament failure. At the very least, even with the addition of a power resistor to fool the Turn/Hazard module while maintaining the ability to detect a LED STOP/Turn element failure, switching to LEDs will lower heat output in the taillight assembly, and based on my research will result in a brighter taillight/Stop/Turn output. Thoughts?

David T

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Guest Mc_Reatta

Now to tackle the 12, 2057 incandescent bulbs in the taillight. Those things consume 2amps in taillight mode (166ma each), and a whopping 16amps in stoplight mode (6 bulbs X 2.66amps each). At least all these bulbs are powered through relays rather than the headlight switch. I am researching LED options, but wondered if anyone on this thread has already found really good LED equivalents? I know that the Turn/Hazard module monitors aggregate current being drawn by the turn filaments and provides a visual clue to the driver (fast flashing IPC turn indicator) if even a SINGLE turn/stop filament is bad. I can install a power resistor in the circuit to fool the module, but that won't reduce the current being pulled through the factory wiring. There does NOT seem to be any monitoring for taillight filament failure. At the very least, even with the addition of a power resistor to fool the Turn/Hazard module while maintaining the ability to detect a LED STOP/Turn element failure, switching to LEDs will lower heat output in the taillight assembly, and based on my research will result in a brighter taillight/Stop/Turn output. Thoughts?

David T

Let's start a new thread for this one. Some thoughts, lots of questions. Think there will have to be some compromises made to come up with an elegant solution.

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Those Simmons relays should probably be reserved for a different project since they seem to have a higher resistance than a standard relay which is not desirable in this circuit.

> Agreed. I have used the Siemens relays before but just for simple switching of a load, like a fan. No problems.

I am going to be mulling over the fact that the relay turns off quicker on the hi beam side then the lo beam side. First thought is it's a slight difference in the two relays, but you said swapping the relays side to side doesn't make a difference. The next obvious thought is the different contacts used in the high / low beam relay and the green and tan signal wire. Might try swapping the hi/lo beam relay with another relay and see if that makes a difference. I'd check the voltage readings on the hot side of each of the new relays to see if there is a difference between them when each relay is activated. Maybe dirty contacts or some frayed wires in the hi/lo beam relay and signal wires are causing this.

!

> I do not know, but after I swapped the filament wires around so the proper beam is activated, it acts exactly the same and it doesn't matter if using the Bosch or Hella relays. My original conjecture was the O.E. hi-lo relay in the console switches from high to low beam when the headlights are switch off, thereby eliminating any voltage on the hi beam signal wire. Maybe the difference in resistance between the high and low filaments? The lights go dark even before the doors start to close.

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Great work guys!

David T: I think some of your calculations in post #60 are unnecessarily pessimized. It isn't a surprise that the voltage is so low with the engine turned off. The battery will sag quite a bit under this situation. When the engine is running, the alternator is working and bringing the system voltage up to 13.7-13.8v. The alternator in our cars is the hefty CS-144 (GMs 'large case' unit). It is a great alternator. It can put out a lot of current at idle. (And there are even aftermarket versions of CS-144s that are tough enough for welding...) When I made the measurements on my car, I saw very little change between engine idling and 'faster'. Less than 1/10th of a volt.

I would opine that McReattas (and now 2seaters) version of wiring the relays, with the HDM inputs connected to the filaments when the lights are off is preferable to leaving them open. I just don't like the idea of the HDM inputs 'floating'. Seems better that they are tied. When I get around to building my harness, that is how I will do them.

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I appreciate all the time and effort you guys are putting into this but one thing I see wrong with this thread is, besides it being 4 pages long, is it is OVER the head of 90% of Reatta owners as to what needs to be done to implement the solution to the problem of the headlight switch having to carry so many amps. I'm not an electronics engineer but I consider myself pretty good at automotive electrical wiring and reading schematics and I'm having a LOT of trouble following this thread.

It would be nice if SOMEONE would write a step by step tutorial on what NEEDS to be done to take the load OFF the headlight switches that can be easily understood by the AVERAGE Reatta owner like me. OR, maybe even better would be for someone to MAKE and SELL a kit that has everything needed with clear instructions on how to install it. Good headlight switches are getting harder and harder to come by so I'm SURE there would be a demand for the kit.

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I appreciate all the time and effort you guys are putting into this but one thing I see wrong with this thread is, besides it being 4 pages long, is it is OVER the head of 90% of Reatta owners as to what needs to be done to implement the solution to the problem of the headlight switch having to carry so many amps. I'm not an electronics engineer but I consider myself pretty good at automotive electrical wiring and reading schematics and I'm having a LOT of trouble following this thread.

Sorry about that. Pretty simple though. The only Reatta wierdness is ensuring that the inputs on the Headlight Door Module are properly actuated - both when the lights are on and off.

It would be nice if SOMEONE would write a step by step tutorial on what NEEDS to be done to take the load OFF the headlight switches that can be easily understood by the AVERAGE Reatta owner like me. OR, maybe even better would be for someone to MAKE and SELL a kit that has everything needed with clear instructions on how to install it. Good headlight switches are getting harder and harder to come by so I'm SURE there would be a demand for the kit.

Basically the typical headlight relay harness layout. For example, see the schematic about half way down Daniel Sterns page: Daniel Stern Lighting Consultancy and Supply. The only real difference is to use SPDT relays instead of SPST relays, and tie the second throw (pin 87a) and the rest of the relay pins as McReattas diagram back in post #42. This keeps the Headlight Door Module happy.

Edited by wws944 (see edit history)
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As to the wisdom of upgrading the stock headlights and wiring... The stock 35 watt low beams, combined of course with the horrible pre-VOL DOT headlight pattern and the voltage loss through the stock 25 year old wiring and switches, to be borderline unsafe for night time vision. In my opinion at least. One of the very first things I did with my Reatta was upgrade the lights to Hella E-code H4s. I have done the same with other cars, as far back as 1978 - when I did the same with my then-new '78 Regal Turbo. (The 6054s in that car didn't even have halogen filled bulbs. Illegal by the then-current headlight regs.)

Many cars built in the last 10-15 years have pretty decent lights from the factory. Between HIDs, projector technology, and the newer VOL headlight patterns, designers can do a better job than what they were constrained by in the past. The U.S. still has inferior headlight regulations compared to the ROW. But it is not as bad now as it was in 1988.

Edited by wws944 (see edit history)
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Guest Mc_Reatta

Patience Ronnie, all in due time. This thread pushed the envelope in building a harness and come up with a design that achieved a livable result and solved the unique hurdles presented by the HDM.

As DAVE89 said wait for the movie to come out.

I had been contemplating making up this harness for some time but was not ready to start building one yet. So I appreciated the research and experimentation provided by the guys who pushed ahead on this.

Until I have made my own harnesses and tested in multiple cars I am not ready to commit to a final design just yet.

So this thread is not to the point that you are looking for just yet.

As to why you would want to undertake this mod, I think the reasons have been debated quite fully. No one will hold a gun to anyone's head mandating that they do this. There will be plenty of folks who will be willing to sell $650+ replacement headlight switches for some time to come. There are a couple on eBay right now.

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