funbooker

I have a '93 C4. I replaced the three white silicone slugs in both headlight motors. It all worked fine for a little while. Then the right light stopped retracting all the way. I used the manual adjustment on the motor but it still had limited range. Now, it doesn't roll up at all. I tested the circuit in the wiring harness and when I turn on the lights, my test light doesn't illuminate. I can jump the terminals on the light itself and get the motor to start.

Yesterday, the left light rolled up and would not roll down. I checked the fuses for the motors and they look fine. I also checked to make sure there was juice to both sides of the fuse and there was. The lights both work.

I'm guessing there's some sort of controller for the motors in the system but I don't know where it is, what it looks like or what it's called.

1984Z51auto

There is a control module, the "Headlight Opening Door Actuator Control Module" located on the inner wheelhouse in the engine compartment, LH Front. It is on the front of the wheelhouse and has two grey multi-wire plugs from the headlights connected to it. That is on a '96, I think yours is the same.

This sounds like a bad ground problem since both headlamp door motors are involved.

Note: if you unplug the Headlight Opening Door Actuator Control Module the FSM advises that you should not plug it back in unless the battery is connected and the Headlamp Switch is "OFF".

You should get a FSM (Factory Service Manual) for yours, a real GM one, as they have full diagnosis and wiring diagrams and you WILL need it if you do much of your own work!

Hot Rod Roy

If the headlight doors don't roll up and down freely by rotating the manual control *****, there's something wrong inside the motors.

The control module should turn off the power to the motors if there is a hang-up inside the motors, so the control module may be working properly.

aklim

Once again the newbie doesn't post his location. Is it something scary? You can always post the next town's location if you are that paranoid. It makes it much easier to help you if someone is near. For example, if you are near me, I might be able to stop by on the way home from work or over the weekend and lend you my spare unit. That will eliminate the guesswork.

Renfield

If it is a bind in the motors or linkage as Hot Rod suggested (and I agree) there's a guy named Stanley Miller on eBay who rebuilds them. Very reasonable. I'm not affiliated with him, but mine both now work thanks in part to Stan.

In fact, they work so well I treated myself to LED bulbs. So nice to no longer cringe when I turn the headlight switch.

Stanley's reman motor assembly looked better than the one I bought from Eckler's (it looked brand new), better price, and his warranty is a year vs. 90 days.

funbooker

I'm pretty sure when I put my test light on the green and gray wires in the light harness, I should see it light up when I turn on the lights. The fact I don't, tells me it's electrical, not mechanical.

I will say that when I first took the light apart, a piece of the mechanism that tilts the light up was hitting the motor. It might have caused a mechanical problem.

The first thing I need to figure out is how to get juice to the light motor. 84Z mentioned a ground problem. Was that a ground on the light itself or in the system?

Hot Rod Roy

It's your car, so you can ignore me if you want.

aklim

Maybe, maybe not. Will it turn in and. Out all the way? If it doesn't, what happens is that it stops and that drives the current draw up. That signals to the module that the light is at maximum travel so it stops power.

1984Z51auto

Please understand that my 1000 mile screwdriver is not foolproof. That said, I believe the ground used by the control module may be bad/corroded. It may also be that the control module is faulty. IF you are able to run both motors both ways with them jumpered to the battery then the control circuit or the module would be the likely culprits. This is where a FSM would help you with wire location and color. Then you could jumper from the plugs on the control module to the headlights and localize the issue further. Where are you at? Close to Denver??

Renfield

This doesn't sound electrical to me in any way. But it took me two years to sort mine out. So what do I know? It's a very complex piece of engineering. I look forward to reading your solution.

funbooker

Thanks for all the suggestions so far. Here's where we are now. I checked the light motor by jumping the terminals and it rolls all the way out and all the way back. I checked the actuator module and when I turn the switch, I get a pulse of juice to the left light and not to the right light, the one that isn't working.

Sounds like the module, right? Well I bought a used module and plugged it in. One light works and one doesn't. Now the light that was broken works when I turn the switch and the one that worked does not work. The strange thing is that the plugs only go in one way so the plug can't be reversed.

Why would the juice pulse come out of my old module and go to the left light, then come out of the new, used module and only go to the right light. I checked fuses again and put the old module back in and the old one works the way it did before I plugged in the new, used one.

I'm thinking the only thing left that could be involved is the switch but why would it activate one light with one actuator module and the other one with a different module?

kenmohr

not allways, I had a cracked gear. It would not rotate manually.

Renfield

That should've been easy to spot when the OP replaced the pucks.

Renfield

Same here. I pointed him to Stanley Miller. He knows more about these headlight motors than friggin' GM ever did.

Keep ignoring advice and we'll all be impressed when you figure out a mechanical bind with a multimeter.

aklim

Only if he was looking for it. I didn't until I shined a light on it for an unrelated matter

PatternDayTrader

Just two years ?

Renfield

When I go to the trouble of disassembling the gear box, I check all wear items. Skip that simple step and you get what you got.

I'm probably the worst mechanic on this forum, but even I know better than that.

aklim

If there's a mechanical bind, wouldn't it have a higher amp draw soonest than it should and thus throw a red flag? IOW opening time is 3 seconds and it opens for 1 second.

Still im not convinced that the new module is working right. I wish he would test it with a known good one or have the module tested with a known good system

aklim

I didn't because i planned to keep the plastic ones as spare. I was replacing them and the pucks. I had bronze gears and plastic pucks ready to go before I opened the motor. Months later i hit the gears with a flashlight and found hairline cracks

PatternDayTrader

Yes.