Hi all,

Son got a new to him 1993; no previous knowledge on car. Trying to fix a few issues. He has no backlighting for instrument cluster.
Fuse good.
Dimmer switch has 12 volts going to it and going away from it.
Adjusting dimmer does not change the voltage, it stays at 12 or a little less.
Bulbs are good at cluster but none have voltage going to them.

I'm early on in trouble shooting the problem, but thougt I would check to see if anyone had a suggestion.

Nothing found yet in archives.

Thanks,

 

The dimmer drives the ground side of the bulbs. Remove dimmer and jumper the solid red wire (bulb minus) to the solid black wire (ground). Turn light switch on, if lights come on full bright the dimmer is bad.

 

Mk378 it look like you’ve been around the block a few time based on your number of posts, I appreciate your response.

A couple of points:

1. The dimmer wires I have are (red with white dashes), (red with white dashes and black stripe), and solid black. If I were to hazard a guess it would be that the (red with white dashes and black stripe) is the bulb low side?

2. The dimmer harness goes to the climate control lights, not directly to the cluster. I say this because if I unplug everything from the cluster, it does not affect voltage on dimmer. My son said he removed a plug off AC lights and the dimer voltage went away.

3. There is no voltage measured with respect to ground on either side of bulb socket at cluster. Seems like I should see 12 volts on one of the sides?

I will double check to be sure every thing I have said is correct and take a close look at the dimmer pot.
Thanks.

 

Do the A/C lights work? The A/C lights are wired in parallel with the cluster lights. If the A/C lights work and btighten and dim, you can rule out the dimmer control.

Practically all the wires have white dashes, ignore them. The red with black stripe wire is the hot side from the fuse. If you ground that, the fuse will blow. The red only is the return from the bulbs.

Measure continuity of the red - black and red wires from the dimmer to the cluster plugs. They should be connected to the same color wire on each end. If not there is a problem with the harness.

 

mk378,

It was the dimmer switch, you nailed it (jumper test revealed the problem).
The dimmer looks pretty simple, maybe 4 transistors about the same number of diodes and an electrolytic cap. The pot only measured about 10 ohms.

Is it common to repair these things, take a chance on used, or do you think it would be ok to permantly jumper it and run the cluster at full brightness? Buying the part new locally would be $125.00 which is totally outragous and thus probably the correct amount.

Thanks

 

Running the cluster at full brightness is OK, though the bulbs will burn out sooner. You could replace the jumper with a suitable resistor to get a preset less than full brightness. I've never tired to repair one but if you know electronics it wouldn't be very complicated. It works by pulse width modulation.