Headlight Problems

[44 Mag]

Was having some problem with my pass side headlight not functioning (open/close) properly. This weekend I deceided to replace the bushings in the motor. After many hours we finally had everything back together, but now the problem. The passenger headlight is operating opposite! Turn the lights on, the housing closes. Turn the lights off, the housing opens. I have tried everything I can think of, but can't get it corrected. There's no way to reverse the wires so I don't know what I've done. Anyone seen this before? Any ideas would be appreciated.

 

[racersedge52]

It sounds like....

It sounds like the wires to the headlight motor, or even perhaps the brushes inside the motor, or the motor control box got crossed up somehow. I have a 94, and I'm assuming yours is fairly close.

I rebuilt my headlight motors about a year ago for the first time and managed to break the solid-state headlight control module. A simple replacement of the solid-state module fixed everything. But I shouldn't have let it happen in the first place. I figure that when I was disconnecting and reconnecting the motors, I somehow caused a short that destroyed or f***** up the solid state control module. In fact, I pulled out the motors again thinking I had done something wrong on the bushing replacement/rebuild. But I could find nothing. Then I got out all the manuals and just started tracing the whole system. It's relatively simple, but of course irritating when you expected your fix to go right the first time.

I had rebuilt the motors correctly. It's somewhat impossible to reconnect the cable the wrong way since most are polarized as I recall. The problem didn't seem to be in the switch in the dash or other wires as I checked continuity on all circuits and everything OK.

Thus, the only thing left was the little 'black box', aka solid state headlight motor control module.

Very simple to replace. On a 94, it's about a 4 square inch and 1 inch high black sealed box that sits on the front of the left front fender well. It attaches by four bolts to the fender.

Your description of the system working, then not working after only disconnecting and reconnecting the headlight motors sounds like what sometimes causes the headlight control module to get wired out. Especially when it does something that doesn't make sense.

Since the control module is solid state, there is no way to repair it at the consumer level that I know of. You just simpy replace it.

They should costs around the $150 range at a good GM parts dealer. That's the cheapest I saw for a new module. There were of course many dealers that were willing to charge more, so shop around.

Also, you might check junk yards for Vette's being sold for parts. You might be able to find a functioning used one cheaper. But be careful here as you can just as easily destroy the circuits in the new one upon installation.

When reinstalling, be sure and disconnect the battery. That way you won't have any surges when you plug the wires back into the new module.

In general, when disconnecting or connecting any normally connected wires in the electrical system, it is a good idea to always have the battery disconnected. That should eliminate the 'short' or 'spike' that causes a lot of these electrical failures.

On mine, when I have problems after fixing the headlight motors, one side just stopped working altogether for apparently no reason. I tested both rebuilt motors on the working side and both were OK. I traced the wires and made sure there were no damage to the circuits. None were found and I hadn't done anything to jeopardise the wires anyway. The only thing left was the 'black box'. It shouldn't have happened, but at least I can pass on this inffo to others.


But before you start spending bucks, trace it down starting with the least expensive fix. Trace the circuits just in case. I doubt it's crossed (or pinced) wires, but it could be.

It's irritating to fix something only to have something else go wrong isn't it!!!!

Good luck.

:Silly

 

[44 Mag]

racersedge52
Thanks for the thoughts. I guess I might have screwed the box up because I didn't disconnect the battery before starting. I would add, I used jumper wires and reversed the two wires for the headlight motor (out of frustration), and the dang thing worked perfectly. Push come to shove, I'll reverse the wires until I can find a replacement black box to try. Thanks again for the assist.

 

[racersedge52]

Good idea!

Good move to reverse the wires and temporarily fix the problem.

That's the thing with electrical problems, especially when the cause is likely coming from a 'black box', solid state type of device.

You lucked out in that you still had power to both lights.

When mine screwed up, only the left side would work and the right side didn't.

In other words, the cause can be similar...overloading, short, spike, etc....but the problem can be really weird and not make sense at all. I.e., more or less like your common computer problem.

But when a sealed hardware module goes bad, the only thing you can usually do is just replace the module.

Probably sounds like you can get along for a while using the jumper, but I would plan to have a backup headlight control module to put in sooner or later. My experience with electronics that start to go bad or don't work as advertized is that they eventually fail all together. And you don't want to get stuck out on 'Submarine Road' at midnight without lights!

Also, your temp fix will give you some time to shop around for the best price on a new or used module.

And when you do replace the module, it's only a 5 minute job.

Have fun.

 

[69MyWay]

FYI

Modules are the same on:

87-88 Fiero
88-Last model Firebird
88-current Vette.

You can find firebirds in the bone yard, and the modules might go for $5. They are on the firewall next to the power brake booster. On the Fiero they are behind the side marker under the left fender/bumper area.

 

[racersedge52]

Oh no.....

Please don't tell anybody that my nice 94 LT1 shares stuff with a ??? Fiero ????? The Firebird is bad enough!

Anyway, that's good to know. I was wondering that since you can knock out the headlight motor module fairly easily while servicing another part of the car, and since our cars are going on 10+ years old, if it would be a good idea to keep a few modules in stock? $5 vs. $150+ is a great savings!

And, if you have experience buying from the 'bone yard', how do those parts hold up compared to new? Typically electronics just either work or not. They don't wear like a mechanical part would.