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Discussion Starter #1
Hi there
So on my 1985 90 the instrument lights aren't working - that's the dials and the illumination for the heating controls - it's not a fuse so I'm wondering if it could be the panel dimmer switch - any ideas ?
thanks
Troy
 

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If the dash is the same as the 99, then the heating control illumination shared a bulb with the glovebox. I just went out to check mine and I had no heater control lights, so I checked the socket in the glovebox and it had fallen out of the holder. My lights were working prior to me pulling the socket back up, then I lost all of my dash lights, but my running lights are still lit. I guess I have something else to fix this week.



277041
 

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What I found out - if all dash lights are out and the running lights work, then it's not a switch problem, so I pulled the rheostat out of the dash and tested the wires - only had power coming in and none going out, so I replaced the rheostat and the dash/heater control lights all work. I had the glovebox out and the bulb holder kept slipping out of the holder, so I used some industrial strength duct tape to hold it in place. Put the glovebox back in and tightened everything down and tested the lights again. Glovebox light is not working and I can't remove the socket to change the bulb because of the tape, so now I have to remove the glovebox again to fix it.

If only one light isn't working, then it's a bulb or socket problem.
 

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Discussion Starter #4
Thanks Doug when you say running lights what do you mean ? And what is the Rheostat?
 

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Lights on all four corners minus the headlights is running/driving lights, or the first click of the headlight switch.

Rheostat = panel dimmer.
 

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This one has zero continuity when testing with an ohm meter. It looks like the little nub on the tripod piece isn't making complete contact around the arc, so I'll clean it up and bend the arm a bit to make better contact.

edit: cleaning, sanding, and bending the tab did nothing for this one. It's been in my car since 2002 and has always worked, but it just died last night.


277066
 

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Discussion Starter #7
Ok thanks for the info - I checked the glove box light and the bulb was in the holder as it should be but not illuminated so I changed the bulb for a new one - no change - checked fuses again all good. Still no lights on the instrument panel. So the rheostat won't affect the the glove box light so these are separate issues ? But I assume they would be on the same fuse ?
 

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Discussion Starter #8
I'm not sure if this is relevant but the front right and rear right running lights aren't working and it isn't the bulbs ?
 

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I think you need to get yourself a test light so you can check your circuits for power. If you have lights for the instrument cluster, you should also have power to the bulb holder for the glovebox since they are on the same circuit.

I don't have access to a '85 90 wiring diagram, but in the early years the front and rear running lights were on the same circuit - left is one fuse and right is another.

The rheostat dimmer will affect all dash lights, including the glovebox light. Use the test light to probe the two wires on the back of the dimmer. Power on only one side means you have power going in but none coming out to power the lights.

277106
 

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Discussion Starter #11
Is my instrument panel lights failure and the running lights on the right side failure connected ? Or completely separate ?
 

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My original thought was no they are not on the same circuit, but I just checked my 73's and the dash lights are on the same circuit as the right side running lights. It was simple to test just by pulling a fuse.
 

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Discussion Starter #13
Wow! So that makes sense then ! So I need to find the reason why I have no right side running lights and no instrument panel - it's not a fuse - so I'm wondering if a fault in the rheostat is to blame - will test tomorrow - thanks so much for you help so far !
 

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Later years had issues with corrosion underneath the fuse panel, so you might want to flip it over and check all the connections.
 

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Discussion Starter #15
Thanks so much for your help - I removed the fuse box and cleaned off the connections with contact cleaner and lights are back !
 

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Discussion Starter #20
I changed the steering wheel from the original used a 99 turbo wheel - have added turbo rear mud flaps and a 900 turbo spoiler - looks good
 
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