92 Fox-no Lighting Issue

G00nies · Oct 12, 2016

1992 fod 5.0l GT
So, instrument cluster lights stopped working except for Hi Beam and other warning lights (which I tested and still work), but no backlighting exists. all fuses are fine. Turn signal indicators are also operational.
Dimmer switch works, but only controls the dome light on/off at this time.
Tested the headlight switch and it ALSO works.

is there a component that I am overlooking? Illumination relay?
Its been a few months since Ive driven the car regularly, but they were operational (last I remember) a few months ago.

Help!

Mustang5L5 · Oct 12, 2016

Year of car?

G00nies · Oct 12, 2016

Mustang5L5 said:
Year of car?

Ha, sorry. 1992 GT5.0L manual

Mustang5L5 · Oct 12, 2016

Ah. Sorry I don't have the specific wiring diagrams for that.

Sounds like you lost the power that feeds the cluster for illumination. have tou pulled the cluster to see if any part of the ribbon circuit tape on the backside has burned out? If I had wiring diagrams I could tell you which wire was the feed from the dimmer to the cluster

stykthyn · Oct 12, 2016

All fuses are fine or appear fine?

G00nies · Oct 12, 2016

stykthyn said:
All fuses are fine or appear fine?

Yes

stykthyn · Oct 12, 2016

Mustang5L5 said:
Ah. Sorry I don't have the specific wiring diagrams for that.

Sounds like you lost the power that feeds the cluster for illumination. have tou pulled the cluster to see if any part of the ribbon circuit tape on the backside has burned out? If I had wiring diagrams I could tell you which wire was the feed from the dimmer to the cluster

It's the pink wire coming from the dimmer iirc

G00nies · Oct 12, 2016

Mustang5L5 said:
Ah. Sorry I don't have the specific wiring diagrams for that.

Sounds like you lost the power that feeds the cluster for illumination. have tou pulled the cluster to see if any part of the ribbon circuit tape on the backside has burned out? If I had wiring diagrams I could tell you which wire was the feed from the dimmer to the cluster

I can MANUALLY power up either side of the cluster with my power probe...

FoxMustangLvr · Oct 12, 2016

You may need a new dimmer switch, I think it controls/flows the power to the cluster?

G00nies · Oct 12, 2016

FoxMustangLvr said:
You may need a new dimmer switch, I think it controls/flows the power to the cluster?

Yeah, that's what I'm thinking but it turns the map light on and off just fine?
That doest mean that it could still be a bad dimmer?

stykthyn · Oct 12, 2016

Before investing in a new one, take yours apart and clean it. The copper contacts can get corroded.

G00nies · Oct 12, 2016

stykthyn said:
Before investing in a new one, take yours apart and clean it. The copper contacts can get corroded.

JUST REMOVED AND CAREFULLY CLEANED THE RHEOSTAT AND CONTACTS. it certainly helped the quirky dome light on/off point, but still no iinstrument cluster backlighting.
Also removed the 5 or 6 194 bulbs marked "ILL" for backlighting and also swapped contacts with known working ones, still no backlights.
BRAKE HI BEAM BATT Check Eng Low Coolant AIRBAG all work just fine. and turn signals

Mustang5L5 · Oct 12, 2016

Trace the contacts for the bulbs back to where they plug in. Using a DMM, test for voltage on the harness when you put the lights on.

If none there, then you shou;d test the dimmer next for voltage out to instrument ILL. I have these diagrams home

G00nies · Oct 12, 2016

Mustang5L5 said:
Trace the contacts for the bulbs back to where they plug in. Using a DMM, test for voltage on the harness when you put the lights on.

If none there, then you shou;d test the dimmer next for voltage out to instrument ILL. I have these diagrams home

Thanks, that would be helpful, I've had trouble finding the proper wiring diagrams going FROM the dimmer TO the cluster. I did check for power and ground at the H/L switch and it checked out

G00nies · Oct 12, 2016

Anyone know which wire to probe FROM dimmer TO Cluster Illumination?

G00nies · Oct 12, 2016

Also just realized that I have NO HVAC control panel back lighting either!
If this helps

Mustang5L5 · Oct 12, 2016

Sounds more and more like the dimmer is your problem.

Highly recommend picking up a 1993 Mustang EVTM off ebay. Every wiring diagram you'll ever need with colors and such for your car.

I'll take a look at my diagrams tonight, but it's for a 1988. May be different

G00nies · Oct 12, 2016

Problem SOLVED! I deserve a whole bunch of ribbing but didnt have a proper schematic for my car and missed the SECOND 5A fuse on the panel once I got a LEGIBLE wiring diagram from PRO DEMAND.
Went right to it and VIOLA!

I went full retard on this one, but thanks for the help. On the Bright side, I learned alot about electrical !

stykthyn · Oct 12, 2016

G00nies said:
Problem SOLVED! I deserve a whole bunch of ribbing but didnt have a proper schematic for my car and missed the SECOND 5A fuse on the panel once I got a LEGIBLE wiring diagram from PRO DEMAND.
Went right to it and VIOLA!

I went full retard on this one, but thanks for the help. On the Bright side, I learned alot about electrical !

I replaced a dimmer and multi function switch because of that fuse. That's why I asked about fuses in my first post.

Mustang5L5 · Oct 12, 2016

Assume you mean the one is slot 13?

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92 Fox-no Lighting Issue

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I want to measure mine. It doesn't look that tall.

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