Hey All,

My LH headlight motor decided to crap out on me, and it was the bushing/relay thingie on the side with the 3 screws that died. Looks like one of the copper tangs corroded and fell off, so now I'm up for a replacement.
My car is an 85 TransAM with the 3 wire motor and I'm in Australia so thirdgens are too rare here to be at a wreckers, so ebay is my only option, and the best deal I've found with international shipping is around $300 for a used one.

Next models up though, 87-89 firebird and 86-88 fieros though seem to have brand new ones for $70 each for the 2 wire versions that use the headlight module. The downside there is people want $500 for a headlight module.

I've foudn some Arduino projects that replicate the headlight module that I can build for around $70 and a bunch of time soldering and reading circuit diagrams but I long story short, I'm wanting to know exactly how the headlight motors work, and if it's possible for me to instead just wire up a simple switch to raise the headlights with power until they're up and then turn off the switch, and then reverse the polarity and do the same to lower.

So.. on to the questions:
1. Do the 2 wire motors require constant voltage to hold them in place, or once it's in a certain position does the mechancial workings hold the motor in place?
2. Once the motors hit maximum travel and are fully up, how long until the power flowing in and the motor under load would it take before damage starts occuring?

For further context, I hardly ever drive the car at night, so the headlights will be used only on rare occasions.
The isolaton relay died a long time ago so the headlights are controlled using 2x SPDT relays per side and another SPDT relay for the isolation relay, all wired in based on someone's design here on the forums and has worked great for years. I also have a custom switch used to control the 12v signal for the headlight motors and low/high beams, so if I'm able to without damaging the motors I'd rather use a 6 pin 3-way switch to control them and just manually shut off the power when they're up/down.

Has anyone tried this before or have some info on the headlight motors to assist?

 

The C5 Corvette headlight control module is interchangeable with my 1989 Firebird at a lower price.

The motors stay in position mechanically. I going on memory here, but I think the headlight module has some kind of over-current detection that shuts off the motors at high load (hit top or bottom). And there is a reversing switch that changes the polarity of motor current to make the motor go up or down.

The functional descriptions and wiring are shown in the GM shop manual, but it does not describe in detail the control module

 

Thanks for that. I had found some designs for an arduin based controller that worked out to about $70 in parts and a whole bunch of soldering, but the C5 guys have found an eaiser approach with $15 worth of 12v timed relays boards wired together so this should work perfectly.

https://www.corvetteforum.com/forums...ol-module.html


Thanks again

 

For anyone else trying to do this, I made a simplified wiring diagram that I could follow to make it and then simplified the wiring a bit to make it easier to track and install.
Top 2 connections are for the wires coming from the headlight motors, bottom ones are common ground, 12 open signal, 12v close signal, and 12v constant.

 

This is a picture of the 3 wire headlight door motor assembly in a 1986 Firebird using the isolation relay, control wiring system.



If yours is the same as this, to which section of this diagram 1, 2 or 3 is the "bushing relay thingy", and has failed?

 

If it just the relays that have failed, they are still available.
Headlight door relay.


Isolation relay.

 

It was the side section, (2) that failed on mine. The plastic had become brittle and snapped and the copper tangs had corroded away.

The DIY module is just a way of upgrading to the newer 2 wire motors which are much more readily available as brand new ones and for much cheaper.
The module costs about $10 in parts to make and takes about half an hour to make, so it seemed the better option than paying around $400 for a used motor and shipping from the states for something that may die after a few uses.