Rebuilt the right motor a year ago, then finally got around to rebuilding the left motor. The second time I tested them, the left one started running on and overheating- got up to 160 degrees before I could disconnect it. I checked the right motor- it was cool...not running on.
The next day I was showing a friend this situation- did NOT touch the headlight switch, but possibly touched the manual knob on the the right motor. As we were leaving the garage, I heard a sound- checked the right motor- 120 degrees and rising!
Let me make this perfectly clear- I did not raise or lower the headlights that day- It just started on it's own! I had also had two incidents of dead battery with no known reason- I now believe that one or both motors were starting and running in the middle of the night.
I decided to install a relay in the RED main power wire which runs directly from the battery to the motors- So that the power is only on when the key is on. Once you shut the car off and pull the key, the headlight motors have no power, so cannot create any problems.
I installed mine in the front compartment, actually mounting it on the lower stud that holds the prop rod- just needed another nut.
I cut the red wire and ran it through the relay, then ran the ground wire to the grouped ground bundle in the harness between the prop rod and the master cylinder.
The actual "Keyed power" wire was a bit more involved; When I ordered my Fiero in 85 I had sprung for the lighting option which installs lights in the front and back compartments- the front one only came on if your headlights were on- and if they were on they lit up your front compartment better than that little bulb- So I hadn't even had a bulb in the socket for 30 years....I cut the brown wire and spliced it to the relay's power wire- then, under the dash, I spliced that brown wire to the window power wire (I don't have power windows)
It might be better to install the relay back by the main junction by the battery- easier to get Keyed power to actuate the relay....
I believe that every Fiero with the early headlight motor system should have this installed- I actually ended up swapping my headlight motors to the 87-88 system- but still installed this relay just to have absolute safety.
The Relay I used is a Pico 5591PT Relay and connector kit- in the connector I removed the center wire which is not used...The relay is available thru Summit for $7

[This message has been edited by cvxjet (edited 12-01-2019).]

I apologize for the extra images- haven't a clue why they are there- I even tried to eliminate them but when I went back all three were there........

OK- hit the computer with a sledge hammer and now have fixed it.......(Basically....)

[This message has been edited by cvxjet (edited 12-01-2019).]

Your showing one wire, in my 86 service Manuel it shows two, fuseable link C and D are they different for each year ?

If you just look at the Headlight door diagram it looks like there are two separate wires, one going to each motor......But if you look at the power distribution Diagram it shows that there is one wire coming off the battery junction block going forward.....This wire passes thru the C100 bulkhead connector on the forward firewall....Then the one wire splits into two which each have their own fusible link, and on to the motors.

I looked at the HL door diagram and thought there was two wires, but then actually looked at the C100 connector diagram and saw only one.....So then I pulled the plastic convo tubing off and looked at the actual wires and saw the real situation.....Then, frustrated at the (Lousy) diagrams, I happened to look at the power distribution diagram and suddenly saw the real situation. Maybe I can get a diagram online and highlight the situation.....

[This message has been edited by cvxjet (edited 07-19-2020).]

Ok , I get it, thanks so much..

Just a bump, I dont think this can be done in the back as that line splits off to a HL function..

I see what you are saying....Rats! When I get a chance I will smoke some more brain cells and see if I can come up with a better setup......

This could be easy, just need to figure out how to get a wire from that relay into the car, but it don't look easy to get through the front firewall, without drilling a hole and I dont want to do that. Any ideas? I have not had a chance to take a good look yet.

PS. I want the power off at all times unless the lights need to go up or down.

[This message has been edited by hunter29 (edited 07-23-2020).]

I used a relay for my pop-ups for the LS4 swap.
The Monte Carlo has auto head lights, but for exposed lights. I had to add a relay to the Monte system to pop the lights up, the Monte system only turns on the light bulbs. I don't remember exactly how I wired the motors, but it was not that difficult.
Now I never even use the head light switch.
The drawback is that starting the car in the garage the lights always pop up. The cool thing is that the lights stay on for about 20 seconds after I get out of the car a night. This helps me see where I am going and what I may step into at night.
I also did a Corvette Tune Port swap (never finished it I sold the engine) that had a head light timer in the blue dingy thing under the dash. This timer could be hooked up to do the same thing to any Fiero.,,,I am guessing?

I had a spare auto dim/temp rear view mirror, so I decided to install it my 88 GT. It’s easy to get lazy when all the modern cars have the auto-dim feature. Didn’t want to drill a hole in the fire wall for the temp sensor, so I ran the two conductor through the rubber grommet used for the radio antennae. The antenna cable is accessible above/near the passenger courtesy light, after you pull down on the carpet -kick panel. I did have to unscrew the wheel line to fish the cable to the front of the car.

Maybe the relay could be installed under the dash- The motor power wire splits off before passing thru the firewall connector...That would eliminate the firewall penetration problem.....I will crawl under the dash tomorrow and see what's what......(Wish there was a Fiero in the JY locally........Then I could pull most of the dash out and have access!

Both good ideas guys..

OK...went out and did some OMB research (On my back).....yep, would have been smarter if I had placed that relay INSIDE near the C100 connector.....(But hey, being stu-pud kept me qualified as a Federal worker for 35 years(Could have gone for Politician but didn't want to get the lobotomy!)

The C100 connector- especially the Red Headlight motor main power wire- is more easily accessed on the inside....and of course this makes it very easy to find keyed power...

Here is a picture with labeling.......

[This message has been edited by cvxjet (edited 07-24-2020).]

GM used many standard plugs and connectors in cars and truck. Some are for outdoor use and some for indoor use. The c500 is an outdoor plug connector and the c100 is indoor and outdoor. The biggest difference is the goo that is used to fill the cavities from water. I used to shop the yards for extra connectors so I can push out the spade wire connectors and push them into the voids of the connectors in the car. This way you can add moore thru wires to your car. Just write the "changes" or modification/additions in a manual.

quote Originally posted by Rickady88GT: GM used many standard plugs and connectors in cars and truck. Some are for outdoor use and some for indoor use. The c500 is an outdoor plug connector and the c100 is indoor and outdoor. The biggest difference is the goo that is used to fill the cavities from water. I used to shop the yards for extra connectors so I can push out the spade wire connectors and push them into the voids of the connectors in the car. This way you can add moore thru wires to your car. Just write the "changes" or modification/additions in a manual.

Rick, I wondered about doing that....It's just that the goo is really.....Gooey! I think the best setup would be to mount it under the dash- It would not be noticeable unless you crawled under there, and easy to find keyed power.

Strangely enough, I was trained as an Avionics tech in the Navy and fixed Aircraft wiring on S-3 Vikings for 15 years at NAS Alameda (Until they found out I was up for a pay raise and had bought a house- then they closed the base!)...But House wiring and even car wiring is very different....The house wiring is like greek to me!

I actually fixed computers at Atari in 1982...Came up with a fix for one problem in 5 days while their head tech spent 2 months chasing it in his lab......But I could not program a computer to save my life!

Cvxjet, good work, my back appreciates it ! This makes it really easy, but you have a 85 right ? I would think its the same for my 86, yes ? I know the wire is red so if there is only one I should be good.

Now we should be able to find key power in the fuse panal, or in my case I think I will mount the switch in the ashtray area so its hidden and maybe grab power from the cig lighter.

You all have been very helpful, thanks so much..

Hi guys, so I looked at what Cvxjet posted and liked the idea, but when I saw I would need to twist myself into a pretzel to do the job I decided to see if there was a way to get through the front firewall.

And I did, the hood release cable has a nice big grommet and its in the right place inside and out. I fished a nylon water line through to use as a conduit and it worked out pretty well. .