HELP! Scenario: '86 GT. Headlights wouldn't work at all. I determined (from the link below) that the car had an '87/''88 headlight upgrade. Did the diagnosis and determined that the control module was defective. Opened the module and verified massive corrosion. Got a new modole, plugged it in and the headllights went up ... and then down. I should have stopped there. The old connectors were corroded so I cut off the old connectors and soldered in the wires to a set of connectors that I pulled when I got the module. Even used shrinkle tubing to seal the solder joints. Put it all back together. The headlights went up, but then wouldn't go down. Went back through the diagonsis in the following link and discovered that the white wire ("C") in the five wire connector doesn't have current with the headlight switch in the "off" position (paragraph 5 of the 87/88 system diagnosis). I have a factory 1986 manual, but the wiring schematic for a 1988 is different. I don't know how to trace the white wire for connector "C" of the five wire connector. Not even sure if there is a fuse for that circuit. Anybody got any ideas? I'm pulling my hair out right now. Just spent half a day at the Pick 'n Pull yard, soldered and resoldered 9 wires twice, pulled the driver's side headlight assembly about 5 times and I'm not getting anywhere.

http://www.fieros.de/en/articles/headlight.html

If you have a spare, swap out the interior light switch. The switch swaps power to the opposite side of the module. One side for up, the other for down.

Sounds like my ex wife. She would never go down...

First ? did the replacement module come from a Fiero?

On the 86 there is power on the white in off on an 88 there is no power on either since they user a different pin off the switch for the white.

Look at the switch on page 1105 of the 88 Service manual download. Then compate to page 994 of the 86 manual download.

There are several different combinations for module control switching depending on if they came from a fiero, firebird, vet or some others.

[This message has been edited by Dodgerunner (edited 05-05-2012).]

Thanks for the replies.
I found a very useful copy of the 1988 Fiero service manual here >> https://www.fiero.nl/forum/Forum2/HTML/114733.html <<
In section 8A-102-2 it led me to check the TAIL fuse. That was it. I was stupid and didn't disconnect the battery when I cut the wiring harness to replace the corroded connectors with the clean replacements that I had just pulled from a 1988 Fiero at a junk yard. As both the red wires are "hot" at all times and the white wire is "hot" with the headlights off it must have shorted when I cut the wires. Disconnecting the battery is probably step one in the entire sequence, but I didn't do that. Put in a new fuse. Headlights go up ... and now down too.

quote Originally posted by GodSend:Sounds like my ex wife. She would never go down...

I think I was married to her.

I have a problem and wonder if it's similar. The right headlight was wired to a toggle switch when we got the car. This is necessary to raise the light. When we disconnected the toggle and wired it as original, the motor sounded like it was running continuously. Does this sound like a bad on off switch?

In your case, I suspect you've got an '86 or earlier car with the first generation headlights (gen1). When the motor doesn't stop spinning it's because the plastic gear inside the motor housing has lost a couple teeth. You can buy rebuild kits for the gen1 motors which include replacement gears at either The Fiero Store or through Rodney Dickman.

The kicker is that it works fine, raising and lowering the light, with the toggle. I'm not certain that the motor actually continually spins when I rewire without the toggle. I can just hear continuous activity in the motor, not necessarily a spinning sound.

Take the guess work out of it for us... what year car? It matters big time.

Sorry 85

OK, so those are indeed Gen1 motors. The best way to troubleshoot the problem is going to be to reinstall the OEM switch and describe what the motors acutally do, since most of the problems with headlights have very distinct characteristics that point to the solution. Having a toggle switch wired into the circuit muddies the waters since there are several ways the previous owner may have wired it up (he may have bypassed several OEM relays for example). Once you get it hooked back up, turn the lights on with the hood open and watch what happens to the knob on top of each headlight motor. If either one continues spinning, then the gear is stripped in that motor. If it does something else, then describe what happens when you turn them on and also what happens when you turn them off.

does it sound like this?

Gotcha, it may take me a couple of days, but will try it out. So, what I get out of this is that it's possible to have your door flip up and down, but still have some teeth shot and have that effect whether the motor can shut off?

Yes. Typically only two or three teeth shear off of the plastic gear which still allows the headlight to work up and down OK except when it reaches it's full up or full down position (one or the other). The gear gets jarred hard enough at the stopping points to eventually cause the teeth to be broken off by the mating metal gear. But try the test to know for sure if that's what's happening.

Cool, makes sense. Well, I just got my sons new clutch pedal from the Fiero store today, so I'll go out and find a headlight rebuild kit.