Headlight motors blowing my Tail Fuse (Page 1/1)
355Fiero NOV 22, 09:32 PM
OK, Been searching the site with various criteria and getting similar results but not have not been able to find my particular problem.

My headlights were going up and down fine for a bit and then I had the passenger side delay going down and then they went backup one more time and would not go down.

I investigated and found the following:
- TAIL fuse blown so I replaced that
- Lights went back up but near the end of going up the TAIL fuse blew
- The fuse is blowing when going up which it should not be connected at all until the switch is put in the off position

Testing I have done:
- Confirmed power to isolation relay both when switch on and off
- both power results were good and powered only in the correct switch position
- disconnected passenger relay so only driver goes up
- Blew fuse
- Disconnected passenger side and put headlights switch on
- TAIL fuse blew near the end of going up

So in isolating each side, I am getting the same issue so I have either rebuilt the headlight motors incorrectly twice (certainly possible) or there is something else going on. The headlight switch is new as well so not sure that would contribute to the issue.


I have a couple original headlight motors I think I will put into the frames to see if my rebuild job is faulty. If this doesn't highlight the motors, any thoughts on what I should test next?

Thanks
Don
IMSA GT NOV 22, 10:00 PM
Did you install a new stereo or do any work to the factory stereo?

If so, disconnect the brown wire from the stereo and try the lights.

[This message has been edited by IMSA GT (edited 11-22-2022).]

theogre NOV 23, 10:49 AM
If that isn't an issue....

Pull C100 next to gas pedal. Like C500 has a Bolt holding it and note bolt is likely SAE not Metric.
This isolated front wiring that may or not blow a fuse.

Because If fuse still blows isn't HL motors or front parking lights.

Go to Amazon and get a short detector kit.
Has a version of flasher can to connect to whatever for power and inductive "meter" that twitches on wire w/ short.

Or get DC Amp Clamp like UNI-T UT210 series (have several types w/ diff prices.) and others w/ smallish clamp to read most amps in cars etc. (Most people don't need to read 200+ amps...)

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

355Fiero NOV 23, 08:54 PM
IMSA GT I did put in new connector for the radio as part of the dash rewire to put in a PISA dash but the radio is not installed yet? I have several brown wires in my dash that are not connected or now into new dash lights as I put in the PISA interior so no longer the same connections as the stock Fiero dash cluster..... I am using the brown dash lights wires in several new switches I installed in a the custom centre console though for interior connected switch backlight to icons in the switches same as oem has.... Will need to trace those to make sure I have them connected correctly in the gauges and switches....

Ogre;
If above search doesn't turn up something, I think I might be chasing a short in the system somewhere like you suspect as I don't blow the TAIL fuse until i turn on headlights and again, fuse blows near the top of the opening sequence so according to my understanding, the TAIL fuse should not even be engaged yet until the headlight switch is turned to off.... More wire tracing to see where I am getting the errant connection. I plan to get the spare motor tonight and connect to each side and see what happens when I turn on the hieadlights as as start. Don't plan to connect other side as I try each circuit.

Thanks for the help
Don
IMSA GT NOV 23, 08:58 PM
Just FYI, the fuse in question controls all this:


Like the Ogre stated above, the easiest way to determine if the issue is with the motors is to pull the C100 connector off of the firewall. That disconnects the entire front end electrical. Then replace the fuse and try the switch with the front end disconnected. If it still blows, you have an issue elsewhere.

[This message has been edited by IMSA GT (edited 11-23-2022).]

theogre NOV 23, 11:07 PM
The Convenience Center is Inside the Cabin under P-side dash on the heater or heat/AC box. Contains Horn Relay, Hazard Flasher and Chime box.
PhatMax NOV 24, 10:15 AM
Or you could go the long road and disconnect all the bulbs and test it. Then add one at a time. A continuity tester would work as well by testing each wire at the bulb socket to ground….you one side will be ground but the other should not. Disconnect battery, test sockets. Turn headlights up manually, test again. Hope this makes some sense…..I’ve had a fever for the past three days.
theogre NOV 24, 11:08 AM
Bulbs and Sockets often have problem of their own and Pulling bulbs etc now may solve or create more problems.

pulling C100 isolates the HL Switch etc that can cause this...
Example: "bad" HL switch can break/bend part inside and short out 1 section to whole thing.

or solves by not blowing.

Either way you start w/ pulling 1 connector.

[This message has been edited by theogre (edited 11-24-2022).]

355Fiero NOV 24, 08:41 PM
Really appreciate all the help folks. Last night I took a second headlight motor setup that had the relay still attached and plugged into the driver's side plug from the isolation relay. The passenger side was unplugged from previous testing. I turned the headlights on and off several times with no fuse blowing and motor working just fine. OK so then looking at: is it the relay or the motor? I plugged the new relay to my rebuilt motor driver's side and again, up and down no issues several times. I did notice that my rebuilt motors are a LOT louder than the one I tested.

I found a second new relay from my parts bin and plugged the passenger side in and I now again, have working headlight motors. Again, louder than the unmolested motor but working. I will be ordering new relays from the Fierostore just to make sure I am good.

Again, thanks very much for all the info and help as I continue to learn more and more about these old cars. Still like them even though they are a bit of a pain....

Cheers
Don