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Suspect the heater adds enough of a load that the up/down module works properly. If the module senses too small a load it thinks the bulb is blown and leaves it up for replacement.

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Probably not a lot of input as this problem has come up for many years, and led lights being a generally expensive change, found the harness to be assumed in the total cost. I am no electrical expert, and went through my own headlight issues burning up expensive headlight switches using 100 watt headlights. At that point extensive factory wiring was changed to make it work, plus relays for load, and about the same time, the harness in question was discovered. To my knowledge as a non expert, the headlight door module must see a ground, such as through the low beam filament to allow the doors to close. A switched ground through a similar resistance value needs to be added to the low beam wiring or it appears just adding the switching side of a relay, terminals 85-86, has enough ground potential to act as a drain and allow the lights to close, usually with some delay.

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23 hours ago, 2seater said:

Probably not a lot of input as this problem has come up for many years, and led lights being a generally expensive change, found the harness to be assumed in the total cost. I am no electrical expert, and went through my own headlight issues burning up expensive headlight switches using 100 watt headlights. At that point extensive factory wiring was changed to make it work, plus relays for load, and about the same time, the harness in question was discovered. To my knowledge as a non expert, the headlight door module must see a ground, such as through the low beam filament to allow the doors to close. A switched ground through a similar resistance value needs to be added to the low beam wiring or it appears just adding the switching side of a relay, terminals 85-86, has enough ground potential to act as a drain and allow the lights to close, usually with some delay.

So your saying to cut the ground at the headlight and just use 2 pins of the relay and it should work correctly?

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4 hours ago, cooldude48818 said:

So your saying to cut the ground at the headlight and just use 2 pins of the relay and it should work correctly?

No. Take a look at the very recent repost of the thread by DS_Porter which has a brilliant and simple solution to the LED light retract problem. The harness turns out to be a universal solution for LED lights and removing the load from the headlight switch which isn't needed with the LED.

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Just be careful if you use the headlight door module modification posted by DS_Porter. It requires cutting the yellow wire going into the module and grounding it.   Although the headlight module sees that yellow wire as a ground when headlights are turned off, there is 12 volts coming from the headlight switch to the module when the lights are on. 

 

If you ground the wrong end of the yellow wire after cutting it you will be making a direct ground to the headlight switch.  Who knows what damage that might do to the headlight switch or the headlight wiring. 🤢 At the very least it would blow a fuse as soon as you turn the headlights on.

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2 hours ago, cooldude48818 said:

Ok. Either I’m blind and not seeing it or I can’t find the headlight control module. I have a 90 reatta made 11/89. 

The module is located below the relay center at the drivers side front of the engine compartment. Best to remove the bolts that anchor the relay center and move it aside, there is plenty of slack. The wire to be cut sounds just like the one I rerouted in a different manner and if so, it is located in the big bundle harness that runs along the drivers fender in the area in question. The yellow wire comes from the passenger compartment through that large harness, and the caution to ground the module side only after it is severed is very valid.

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I would buy the relay harness as it is better for your car's headlight switch and also if some other "electrical" issue should rear its ugly head you will know that your harness is original and the likely culprit is a module or end component.

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Just wanted to thank everybody for their help. I found the module and the wire and cut and capped the wire going to the headlight switch and led the wire from the module up to a factory ground spot. Headlights work like they are suppose to. I installed a fuse in the ground wire just in case. Probably no need to do that but just in case lol. I'm sure I'll be back for some more questions! Also there was another spot on this website that mentioned the 5 or 6 splices under the passenger side carpet that go bad and wasn't allowing my dome lights and a few other things to work. I got that mess straightened out to! You guys are awesome! Thanks again!!

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There are splices under both seats with similar issues. If seemingly unrelated things don't work, especially on the drivers side, take a look under the other seat. I had drivers door courtesy lights, door locks operated by the trans shifter and the trunk lock at the rear, sure looked unrelated to each other but thanks to this forum, I found the problem. Oh yeah, I think the inner rear turn signal/brake high filament light bulb didn't work on each side either. The 90-91 rear flasher system is different in that the outer two turn signal bulbs are operated from the dash area as usual, but the third bulb, the inner one, is operated via a relay inside the trunk on the passengers side front. If no power gets to the trunk mounted relay, the third bulb on each side won't flash.

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Yup. I tore the interior out and had to redo every single splice pack on passenger side. All driver side ones were good. My car had damp carpet and took 3 days to dry it out with a furnace blower lol. Now I’m sure it’s on here somewhere and I’m not seeing it but now the next task is the cruise control. It doesn’t work at all and when I first got the car, I could read codes by using the off temp up buttons but now it won’t let me do that. So I got into the bcm with my scanner and it shows the cruise switch and all of its buttons working as well as the brake switch turning on and off. So I went out to my parr’s reatta and took the cruise servo out and swapped them but still doesn’t work. Nothing happens when I hit the cruise. No lights no nothing. 

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This may be weird to most here but on the just departed Black '89 my cruise stopped working. I swapped out servos [I had 5 of them] and no luck. No codes either, but on a whim i swapped out the headlight switch and the cruise worked.

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Just a note but many things can cause the cruise to drop out. Was driving my 90 Bonneville up north and when the outside temp hit 45F the cruise suddenly dropped out. Seems the thermostat was stuck open and when the coolant dropped below 158F, it went open loop and the cruise control dropped out. Never a problem in Florida because was garaged.

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  • 2 weeks later...

I re-posted this on March 20 but I will insert it here because it is directly relevant to this post...

 

See page 8A-102-0 in the '89 FSM

On the Headlight Control Module connector C1 terminal C I cut the wire and capped the wire leading away from the HCM connector. I connected a 16ga wire to the severed wire C coming out of the plug and I ran that wire to a good ground.

 

The LED bulbs I chose are much brighter than any incandescent and well worth this modification. Any type bulb can be installed and they will retract just fine.

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  When I converted to LED headlights I wanted to understand and solve the problem of the lights not retracting because I was looking to benefit from the reduced stress on the

headlight switch. It seemed like adding a relay harness was redundant although it is still the best fix to reduce stress on the switch regardless of which headlight type is selected.

  When I selected the LED headlights to install it was more than two years ago and direct replacement rectangular  lamps were not readily available. I settled for a pair that is not yet DOT certified. They have three rows of four large bright LED's. Six turned on for low beam and all twelve for high beam. Way brighter than the best stock halogen or regular incandescent. The problem however was the low beam pattern was the same as the high. I was getting a lot of drivers flashing me due to the low beam wide pattern.

  So I ended up partially blocking the six low beam LED's with a carefully cut piece of electrical tape. Most all the light above horizontal is blocked. No more drivers flashing me and the pattern is still plenty bright. I think my high beams are the brightest on the road.

  I leave my fog light switch on at all times for general safety and also because it looks sharp with the front and rear parking lights lit up. All are LED;s and it took a lot of trial and error to find the best brightness and color. I would like to share part numbers but they all came from chinamart which is all just a crapshoot. And now I am hoping I never have to buy anything from china regardless of any perceived benefit......I hope they ....  oh I can't say that

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I ended up cutting and capping the wire and leading other end to ground. They work great now. If I could get my cruise control fixed it would be awesome. Tried new/used servo and that didn’t do anything. I may try the brake switch next. Good thing to have is an extra parts car lol. I was lucky enough to buy 2 of these cars same color and one day apart for $800 for the both of them. Loved the one I had when I was younger! Can’t pull any codes from the onboard diag because all it will do is the lights on the dash flash really quick and that’s it. I’m thinking about switching bcm’s to see if that helps. The parts car won’t go into diag mode as some of the heater control buttons don’t work. 

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  • 2 weeks later...

Just wanted to update you guys. I got the cruise control working. Found a test procedure for the cruise servo under the hood and it tested bad. Bought a new one for $100 which I thought was cheap enough and installed it and it works great. It’s bringing back a lot of memories for the one I had back in the 90’s. Thanks to all that have helped me on this journey to get a great car going and back on the road again!! 

37A50328-220B-488F-AF18-E4765212BB04.jpeg

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  • 2 weeks later...

"LED bulbs I chose are much brighter than any incandescent " - minor quibble: much difference from a stock 37w, not so much from a 55w  SilverStar Ultra (been using for twenny yar) or Philips +130.

I  an concerned that the little fan will fail and not know until things melt.

 

ps COOL: that is the advantage that the drivetrain and accessories (like the cruise control and the ATC fan control) were used in millions of cars.

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  • 3 weeks later...

Hi. I recently purchased a 1990 Reatta coupe. I see a lot of posts on numerous sites regarding headlight doors not functioning properly along with advice and available replacement/rebuilding parts. I've found mechanical & electrical advice but what I have not seen is what the problem may be if the headlights come on but neither door opens and the knobs on the motors do not spin. I can raise the doors by manually spinning the knobs. Any help would be appreciated.

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If both headlights fail to open, I would suspect the headlight module. Full description & diagnosis is in section 8A-102 in the factory service manual.

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Since you recently purchased the car and do not know the history...........

First look at the relay center in front of the air cleaner.....the previous owner may have pulled the fuses because there were mechanical problems.

 

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