chicago_fog

My 1985 SEL 500 just lost the back-lighting for the instrument cluster.
The radio does not work but 'back-lights' when I turn the lights on. The instrument cluster used to back-light but it has just stopped. The back-lighting for the temperature controls has not worked since I have owned the car. The heater also randomly stops blowing warm air. If I pull over, turn the car off and start it back two or 3 times it will instantly blow heat for a random amount of time and start blowing cold air. I suspect these are all related as they seem to share a common fuse (I think). -Warning buzzer (for lights, seat belt) are on the same fuse works fine and if I pull the fuse the radio back-lighting stops working when the lights are on)
At this point, heat is intermittent, not back-lighting for instrument cluster and temp controls...no radio...oh and the digital temp display randomly works too.

ANY thoughts or help would be appreciated!

(new alternator, belts, battery and fuses)

BENZITCH

1st the heat.

Sounds like a monovalve gone bad. Easy fix and not very expensive.

Do a search on monovalve replacement.

2) Instrument lights. Try playing with the rheostat for the intensity of the instrument lights. Sometimes it gets hung up from resetting the trip odometer.

chicago_fog

Awesome! I did accidentally hit the trip reset yesterday hours before this happened.
I'll try it and post the results.

Any thoughts on the center column? Nothing back-lights for the temp controls and the radio does not work but when I turn the headlights on the LCD display on the radio glows but displays nothing.

I also noticed something odd today. When the fuel light comes on it "flickers" whenever I hit bumps in the road...it almost constantly flickers -here in the land of rotten roads (Illinois) Bad ground going to the cluster? Where would I look to check the wiring\ground?

Thanks so much!!!

BENZITCH

Center column and or stack most likely is a bulb.
It uses a sort of fiber optic set up to illuminate the stack.
The radio could just be dead, but I am not sure.

Do you have lights on the shifter gate?

chicago_fog

There are no lights on the shifter gate.
Can you tell me where the light bulb that illuminates the stack is located so I can replace it?
Thanks for the help!!!

Berde

Check the fuse also since all those things work on the same fuse. If not could be a bad connection or just a wire going bad.

chicago_fog

BERDE: in my original post it states the fuses have been checked and new.

chicago_fog

Thanks BENZITCH. The rheostat was gummed up. I cleaned it and the back-lighting "flickered" so I pulled the cluster out and reseated the main harness and everything works perfectly again. Thanks!

I'm going to check the monovalve this weekend.

BENZITCH

The fuses should be the copper fuses and not the aluminum ones.

The copper to copper fit in the fuse box is a better metal match, than the aluminum to copper that came with the cars.

BENZITCH

Your welcome
Glad it worked.

Check out my post on the fuses though. Changing from aluminum to copper has gotten rid of a number of electrical gremlins for me.

chicago_fog

BENZITCH,

The monovalve replacement kit has been purchased and installed. I know have heat 100% of the time.
Thanks again! you are 2 for 2 -100% THANK YOU!!!

BENZITCH

Maybe I should open a 126 specailty shop.

Your Welcome.

Do yourself a favor and get the copper fuses. there like $7.50 or so at Mcparts stores.