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Running Light/Signal Light Dilemma ‘37 Special


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With the Light Switch in the off position, the running lights (now wired as signal lights too), work perfectly and are bright.  When I turn on the light switch, the running lights dim significantly and, when used as signal lights, can hardly be seen. 
has anyone else encountered this dilemma? Possible solutions/ideas would be greatly appreciated. 
BRodd

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A lot of variables... I am assuming you have converted the bulbs to dual filament bulbs. What type of turn signal switch are you using? Different ones require different wiring setups. It is also possible that you have the wiring reversed on the added dual filament bulbs and you have the brighter filament wired to the parking lights and the dimmer filament wired to the turn signal wiring. If you are trying to use the original single filament bulbs, you are going to have problems until you switch to dual filament bulbs and sockets.  

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Thanks for all your responses. Yes. They’re dual contact 1154s, Ba15d. I also checked the  new, dedicated ground wire; all good. When I turned on a signal light, I noticed that the smaller filament blinks on and off (very brightly, I might add).  As I pulled the light switch to the first stop (driving lights and taillights), then the second stop (headlights), the longer filament came on progressively dimmer. The blinking signal light filament also became weaker.  Do I have the hot wires reversed as Matt suggests, or is there something else I need to consider?
 

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What make and model of turn signal switch are you using? Do you have a wiring diagram for the turn signal switch? If not, how many wires (and what colors) come out of the switch? 

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I bought a new 7-wire signal switch online several years ago and took its mechanism and placed it in the housing of an old KD. Of course, I can’t find any of the paperwork on the new signal switch.
The wire colors are red and yellow (which go to the flasher), orange (to the stop switch), light blue and green (to the front lamps), and black and dark blue (to the rear lamps).  I also have the hot wire from the light switch to the flasher and a ground wire.  

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I need to do some research on a few different flasher wiring diagrams that I have seen, but off the top of my head, if the turn signals work correctly with the headlights off, I would try removing the wire from the light switch to the flasher and use another source of power to the flasher circuit and see if that changes anything. 

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Great idea.  I’ll certainly will give that a try. The power line off the light switch to the flasher has a fuse on it. I don’t recall the size, and I don’t think it’s an issue, but thought I’d mention it. When I bypass the light switch to the flasher, I will put the same size fuse on it. 
BRodd
 

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Ground those sockets in the parking/signal lights. If necessary run temporary ground wires all the way back to the battery or chassis for a test, Having done that, if the small filament blinks as a turn signal, the wires at the parking/signal bulb are reversed.

 

As for the 7 wire switch, it is fairly safe to say all the remotely modern ones work the same way. Power is fed to the switch from the flasher and also from the brake switch as you have noted. The magic is in the rear light hookup. The rear filaments are only connected to the brake light switch by contacts in the turn signal switch. When you turn a signal on, the switch disconnects one rear bulb from the brake light switch and connects it to the flasher. On the front, the switch just connects the big filament to the flasher.

 

With a little testing you can probably verify that the switch is wired correctly even if you don't know the color code. If you add it up, it's 6 wires. Four large filaments, one at each corner of the car, power from brake switch, power from flasher. The seventh wire is just to a "pilot" bulb in the switch to show you that the signals are on. It goes to the third flasher terminal. The pilot bulb must also be grounded, usually by grounding the switch housing.

 

To recap, the 7 wires are:

 

Power from flasher, flashed (but wont actually go on/off unless the switch connects bulbs to it)

Power from brake light switch (only live with pedal pressed)

Right Front

Left Front

Right Rear

Left  Rear

Pilot (this wire goes to the third terminal on the flasher)

 

Edited by Bloo (see edit history)
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I have a dedicated ground wire for each of the 4 corner bulbs that connects to the ground bolt on the starter. I think they’re grounding well, but will double check the connections.  I’ll also reverse the wires to get the larger filament to blink on the front (fender lights). Can I infer from your comments that the turn signal in the taillight is also the larger filament (as in the front)?

BRodd

 

 

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A Quick Recap

- Taillights, brake lights, running lights, and directionals (with a new flasher) are now working properly. - - However, when the light switch is pulled to the first stop, all four corner lights dim.  -  - When the light switch is pulled out to the second stop, all four corner lights dim significantly. 

Update

1) All bulbs & wiring are confirmed correct;

2) The ground wire to the headlights are working well;

3) An alternate power line directly from the battery to the flasher was tried (and not through the light switch); all four corner lights continued to dim when the light switch was pulled;
4) I tested the battery and it registered over 6 volts;

5) With the engine running, the generator, the voltage regulator, and running lights each registered more than 6 volts

6) With the light switch pulled and engine running, the headlight and running lights registered only 4.75 volts

Next Steps

I will check the continuity of the light switch 

Any other suggestions?

Again, my thanks to everyone for your ideas; they are greatly appreciated. 

 

 

 

 

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@Bobby Rodd, I have the same question as @Rock10.  With the light switch pushed all the way IN, you should have NO lights on. Buicks do not have tail and running lights without the light switch pulled out. What you describe still sounds like a ground problem with the headlight bulbs. As you have checked and rechecked that, the light switch and/or wiring seems to be the most likely problem. The way I would check this is with a jumper wire. With the light switch pushed in all the way, jump from battery positive to each lighting circuit and see how things work and if the lights are bright. I do not remember from earlier in this thread if you have a new wiring harness or have modified a stock harness. In any case all the lighting circuits except brake lights start at the light switch in the dash so that would be the place to start!  Keep us posted. Also, Buick lighting in 37 was a strange duck. If you do not have a service manual you NEED one. It has the wiring diagrams and wire routing diagrams you will need.  Best Luck!!

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Posted (edited)

Well my first guess would have been the grounds at the corners, but you have dedicated ground wires, right?

 

If it isn't that, there must be a resistive connection somewhere between the regulator BAT terminal (source of power when the engine is running and the generator is charging) and the light switch (where the headlights could drag the voltage for everything down).

 

You should probably have the engine running at least at a fast idle if not 2000 rpm or so. At just idle the generator wont keep up and dimming is probably normal.

 

That said, The wiring probably runs from the BAT terminal on the regulator, to one side of the ammeter. and then continues from that same side, on to the circuit breaker, and then the light switch. My money is on the circuit breaker, it might need it's points cleaned. I would probably run the engine at 2000rpm or so for a couple of minutes with the lights on and things dimming down, then go around feeling all the connections and see what gets hot. Don't burn yourself. Maybe start with a glove if you are not accustomed to touching hot things. The spot where the voltage is getting lost is likely to get hot.

 

One caveat, the circuit breaker is probably going to develop heat even normally with a bunch of lights on, so don't be fooled by that but maybe clean it's points anyway. It may be hanging on the back of the light switch. If the heat shows up somewhere else, like at the back of the ammeter, or some other terminal at the end of a wire like at the voltage regulator, etc. then there is a bad connection where you found the heat. The points in the light switch could be dirty too (and it might get hot). If you take the light switch apart to clean it's contacts, there are 3 triangular pieces in there that look the same, but are not. Keep track of which ones went where.

 

Edited by Bloo (see edit history)
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37_R_C, et al

Sorry for the confusion.  You are correct, with the light switch pushed in, there are no lights on. 
With the switch IN and the engine not running, I applied the brakes, and the brake lights work brilliantly (pun intended). I, then, test the signal lights; they work appropriately and brightly. Then the signal lights are tested while the brakes are applied — all work appropriately and well. Finally, I run the same tests with the engine running; all lights work brightly and as they should. 
Light Switch Pulled Out to the First Stop

With the engine running and the light switch pulled out to the first stop, the running lights and taillights come on appropriately and with good brightness. I then follow the same test sequence I described above (I.e., brake lights, then signal lights, then brake lights and signal lights together, etc.). All work well. 
Light Switch Pulled Out to the 2nd Stop

With the light switch pulled out to the second stop, the headlights, along with the running and taillights, are on. However, now all lights are greatly diminished including the headlights and the signal lights when tested. 
The car has all new wiring (courtesy of Harness Unlimited) so I then checked the connections (positive and negative), the bulbs, and the dedicated ground wires I added. I made sure the contacts were clean  and had dielectric grease on them. I then checked the voltage output on the battery, voltage regulator, and generator and the voltage at the light terminals. All were over 6.13 volts except when the light switch was pulled out to the second stop - the headlight terminals were at 4.75 volts. I even disconnected the signal switch which I had put in, but the results were the same. 
i, too, was thinking that there might be corrosion on the light switch contacts. I had cleaned out the contacts in the light switch before I put in the new wiring harness a year-and-a-half ago, but I’ve been working the switch in and out a little, but have not seen any improvement.  
I’m now going to look more closely at the voltage regulator as Bloo suggests. 
Once again, thanks to you all for your willingness to help me work through this challenge. 
BRodd

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Posted (edited)

So as I understand it, everything is OK until you turn the headlights on? That's with the switch in the second position. Are you sure the headlight bulbs a 6 volt? Sorry if you already answered that.

I would disconnect the headlights from the light switch and see what happens.

Edited by Rock10
More info. (see edit history)
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A couple more thoughts.

What happens when you click the dimmer switch?

Does your car have the special cross aimed brights and the 3rd position light switch?

Is the wire to the switch heavy enough? Not sure what gauge wire was used originally.

Again, sorry if you already answered.

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Posted (edited)

Since you have installed a new wiring harness, I would suggest you recheck all of the connections in the wiring in the headlight circuit. Since everything works with the fender lights on but the problem occurs when the headlights are switched on, it is likely that something is wired incorrectly in the headlight circuit. There are a lot of terminals on the headlight switch. It is easy to make an error when wiring it up. It is also possible that you have switched two wires on the dimmer switch, grounding the headlight circuit. 

 

If all of the wiring is correct, I would suggest you try another headlight switch. It is possible that you have a problem in the switch from when you opened it up to clean it. Something is shorted to ground somewhere. Either incorrect wiring connections, a bad dimmer switch, or a bad headlight switch are about the only possibilities that I can think of with the additional information that you have posted. 

 

If you need another headlight switch, I suspect Dave Tacheny would have one available. 

Edited by MCHinson (see edit history)
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With your battery fully charged, and the engine run up to 1500 or 2000 rpm so the generator is sure to be charging, your system voltage should be more like 7.5 volts at room temperature (check the shop manual for the real spec).

 

It is normal for there to be some loss on the way to the headlights, but it sounds to me like 1) the charging system might not be working and 2) there is probably too much loss somewhere between the voltage regulator "BAT" terminal and the stuff hooked to the light switch.

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Could the headlights be in series? just typing out loud. If the ground is on the filament side instead of the common of the lamps you will have weird things.

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The headlights being in series would dim the headlights, but not the running lights. I would be extremely suspect of the light switch since you had it open. Like Bloo said, the internals of that switch look very much alike, but are in fact different and make a difference.  I have dug out my service manual and am looking at the stock wiring diagram. There is a circuit breaker on the light switch. The first thing to check is the power to the light switch and through the breaker.  There should be a wire from the amp meter to the light switch. This is the battery power to the lighting circuits. What is the voltage on this wire, at the light switch in all positions of the switch? It should be close to 6 volts in all positions. If this is the case repeat the test while measuring the voltage on terminal #12, I think. The diagram is very unclear as to how the switch actually works. What I am trying to have you measure is the loss through the breaker. It will be worse when the headlights are on low and even worse on bright. If you can bypass the breaker, FOR TESTING ONLY, do so and report back!

   With what you described, in detail 👍, the problem almost has to be either the breaker or the switch. My suggestion to leave the switch off and jump from battery positive , switch terminal #1, to each switch terminal and record the results, is still a fair idea, but the real question is what is happening with the breaker and switch in general.  Because the running lights dim when the headlights are turned on it really points to the breaker or a main power connection at the switch.  Keep us posted!!

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As I re-read all of your responses, I realized that I forgot to mention that I replaced the headlight bulbs with 6 volt sealed beam headlights.  I even switched out the sealed beams to insure that the problems weren't in the headlights themselves.

 

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Agreed 37: My thoughts were to find the trouble with the headlights first. Might put you on to the other problem. If they are losing that much power through the switch and breaker something should be getting pretty warm.  Yes, try bypassing the switch and put power direct on the headlight circuit. that will isolate if the issue is under dash or outside. At least, on this car, you won't fry the computer if you put power somewhere you shouldnt.😁

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Are you sure you have the three pins in the right order on the sealed beams? The pinout does not hold true for the different sizes and shapes of sealed beams. 5-3/4 is definitely different than 7", and if you have 7" with an H4 conversion, the pinout is like 5-3/4.

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  • 2 months later...

After several months of trying to find the cause of my headlight/running light dilemma, I think Ive narrowed the problem… but still would appreciate your help. 
With all the lines disconnected at each of the two headlight terminal blocks, I checked the voltage coming off each wire. 
Light Switch at the 1st Pulled Position 

With the engine off and battery connected, the running light wires each registered 6.18v.  

All other lines show no voltage.

Light Switch at the 2nd Pulled Position

At the second pulled position, the right and left running lights and the right and left bright headlight lines individually registered 6.16v. All other lines, (I.e., the dim headlight lines) showed no voltage.

However

When I depressed the floorboard dimmer switch, only the left dim headlight wire registered voltage (6.15v).  The rest of the lines (that is, the 2 running lights, the right and left bright headlights and the right dim headlight, each registered only 0.12 volts. 
 

I would greatly appreciate any observations or thoughts on where I should look/go from here. 


Testing the Dimmer Switch 

With the battery wire connected to the “Batt” terminal on the dimmer switch, power goes through only one of the two remaining dimmer switch terminals. When the dimmer switch is depressed, the power is blocked from this first terminal and is transferred to the remaining second dimmer switch terminal.  Is this how the dimmer switch is supposed to work?
Or, when the light switch is in the second pulled position, should power always go to one terminal (dim) and then off/on to the second (bright) when the dimmer switch is depressed?

BRodd

 

 

 

 

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Off the top of my head, I don't know how the dimmer switch circuit works but if you have two headlights on when in high beam mode, and one goes out when you activate the dimmer switch, you appear to have a bad dimmer switch or else you have some wires that are not connected properly, or there is a problem inside the headlight switch. 

 

If it were me, I would install a new dimmer switch. If that did not solve the problem, I would check all of the wires in the headlight circuit again. If the problem still exists, I would replace the headlight switch.  

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It sounds too me more like a wiring issue. You are correct on the dimmer. It switches between one terminal and the other. If you have one wire with 6 volts and none of the others in the dim position, where is the disconnect? Normally, in this age of car, at least here in Canada, the running or parking lights come on at the first click, and only the headlights on the second. Tail lights on all positions. 

Initial posts says park lights are used as signal lights. How is this accomplished. You cannot really use the single filament as both. It needs to be modified to take a dual filament bulb to work properly. That, or completely eliminate the park light function. 

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Hey @MCHinson, can a 1937 beam both lights up and down in the third (not fourth) headlight switch position like a 1938 can?

 

1 hour ago, Oldtech said:

Initial posts says park lights are used as signal lights. How is this accomplished. You cannot really use the single filament as both. It needs to be modified to take a dual filament bulb to work properly. That, or completely eliminate the park light function. 

 

I'm pretty sure he changed sockets and it was covered in an earlier post. He mentioned 1154 bulbs.

 

 

Edited by Bloo (see edit history)
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Thanks to all for your recent responses. I have ordered a new dimmer switch. My suspicion is that the light switch is the culprit, but will continue to double/triple check the wiring and connections.
The running lights were converted to 1154s, as OldTech said, and are working well as running and signal lights. 
BRodd

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It is fairly common for a Multibeam system like this to drop one headlight due to a headlight switch problem. There are 3 triangular shaped contacts inside that look the same but are not. One is slightly bigger. People get them back in wrong. If you search for old threads about "Guide Multibeam" you may even find pictures. I do not remember for sure who posted them, but probably @Gary W .

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