After 10 pages of advanced search I've decided to start this thread.

Let me walk y'all through it. 90 formula, previous owner hacked the loom and added wires that didn't need to be. I worked on straightening everything out with success until now. Starts out that the headlights would not open. They lit up but, would not open. I do my research, probe the orange wires and discover they have no power. For my own reasons, I choose to open the control module first and find everything looking good except, the circuit board looks bubbly (like the shellac is starting to peel from the board) but, the solder points look beautiful. I put it back together, found 2 blown 15A fuses in the convenience center under the dash next to the radio. Replaced them so, now my orange wires have power. I test the grey and green wires at the module. Grey wires are constantly hot, green wires are switched for about 15 seconds when you turn the lights off. Makes sense to me, assuming that power supply only runs long enough to close the lamps. Yellow wire and brown wires have power when headlight switch is turned on. Ground probed backwards shows a connection. Still no luck.

I then probe the green and grey wires at the actuators, on both sides of the connectors and find the same results as I did at the module but, still no result. I had already ordered new motors/actuators so I decided to install them anyway. Just before I did, I started getting some movement on the right side (too late, I'm already committed to the R&R job).
I replace the actuators. Both sides now fully adjust at the **** however, left side still doesn't open and right side opens and closes partially - if I adjust it all the way open, it goes down about halfway when I shut off the lights. When I turn the lights back on, it opens back up most of the way but, not quite. In other words, the headlight does not travel all the way open or closed and it seems to travel further when closing, than it does opening. In essence, I can get it to close all the way, if I turn my headlights on and off about 10 times but, it's not reopening all the way, without the ****).

I have studied the wiring. All appears to be proper electrically. I did not use a multimeter, just a simple test light. I can't imagine a simple headlight switch would cause this problem and I'm ready to condemn a faulty circuit in the board of the module. I wanted to bounce it off of some of you before I do.

Thanks for reading. I look forward to your replies (and criticisms)🤣🍺👍🇺🇸
​​​​​
​​​​​​​

 

Ok, so I tried jumping off each pin of the motors using the top terminal of my battery (Group 75 DT) and oddly, I got nothing. So I forked the end and tried to jump both at the same time. Again, nothing. Plugged them back in and back to the same old RS goes up partially, LS does nothing. I whipped out 'ye olde multimeter' I tested the battery first, since it's been sitting without being charged, while I troubleshoot this thing, and voltage came back 11.52. Ok, so it's a bit low.

I started probing wires at the connectors and at the module.
In short, everything came back 11.48 volts which, is pretty close to the battery at this point. Everything that is, except the brown wire. That came back exactly a volt short at 10.48. checked the ground in reverse and it showed 11.48.

I doubt the brown wire is supposed to be lower than the rest so now the question is, is the headlight switch bad or is the module bad? Also, do these motors/actuators have independent ground or, do they ground out through the bolts that attach them to the doors?

I'd really hate to drop $150 on a new module only to find the same problem. I'd also hate to waste money on a headlight switch to find the same problem. Can anyone tell me what I should be looking for when testing the headlight switch?

 

The motors are just a motor. 12v+ one wire, ground the other and they run. To go reverse, flip the polarity. What controls everything on the later birds is the Guide control module. I've seen all kinds of hack fixes and none of them work. If the wiring is hacked up, fix it first, then try a good module. If the motors run, and the pellets are good, 9 times out of ten the problem is going to be the module. The rest is in the wiring, the switch, and the high beam switch.

There are charts in the Service Manual that explain how to test and troubleshoot the system. I'd suggest looking for older threads where those charts have been posted, or find a copy of the service manual.

 

If the wiring is hacked i would honestly install an unmolested headlight harness. If you need a headlight module I have spares. I have a 90 formula as well.

 

Wiring attached to the old motors was hacked. Those are gone. Wiring in the header panel and everything running up to the module on the firewall looks good and untouched.

Alright, then. I don't really care to buy a used replacement. So, I'll update you guys when the new/reman replacement gets here.

 

UPDATE:

So I found a boneyard close by that one single 1990 firebird in their invetory.. I pulled it, paid the man $10 and got it home. As soon as I plugged it in, the left side went to down. I ran to turn on the headlights with the excitement of a schoolgirl at a Justin Beiber show and voila, they both go up all the way, they both go down all the way and in perfect timing.

Now I know I said I was gonna buy one new but, I got lucky for $10. Punkmaster, send me a PM with a price tag w/o shipping. I have a feeling this one won't hold out forever and it'd be nice to have a spare.

Drew, I appreciate you chiming in because you kind of confirmed what I was already thinking. I've had 6, 3rd gen camaros but, this is my first firebird so the headlight thing was a totally new experience for me. I know there's a ton of posts related to this problem chewing up server space and believe me, I sat here for 3.5 hrs reading through 10 pages of old posts. None of them had my exact symptom (though a few came close) and most of them were abandoned with no confirmation of a fix. So I wouldn't mind if an Admin closed this thread as SOLVED as we have a conclusion, BAD MODULE!

Thanks again guys. You're the reason I love this site.

 

I think my first experience with the module was within a few months of buying my 91. I walked out of work one night and one of the headlights was up. An *** pounding at the dealership counter later, I was back in business. Since then I hoard every module I find. The transistors like to melt, and the multi-function relay likes to fail, the solder joints like to crack. It's pretty much a ticking time bomb, but I haven't needed to change mine since I replaced it. My second 91 Firebird never had a problem, but my third had both motors in need of new pellets, it's module was good but the spare harness and module I got from a parts car awhile back had the harness hacked so both motors were wired into one side of the module, which promptly melted the module, so it needed a new harness and a new module. Oh well, win some, lose some. The earlier cars have more complicated and noisy motors, plus a system of three relays that's totally crap. In comparison the later module and motors is great, there are only a few things that can fail.

 

Every fourthgen fbody i see i pull the modules too. 90-02 all work together.

 

Some of the earlier modules are supposedly different. But from comparing the wiring diagrams, I don't see how they could really be different. Anyway, there are lists online of which interchange. There were Sunbirds, Buicks, Corvettes, Fieros, all with the same module(s).