Instrument cluster lights not working. Any ideas?

[JeffM]

Just posting to see if you guys can think of soemthing.. A couple months ago, the instrument panel lights shut off. I checked the fuse, and it was blown. I replaced it, and it blew immediately again. I then saw smoke coming from the dimmer/cabin overhead light dial.. I ordered a new dimmer switch, thinking that was it.

Put the new switch in, and a new fuse. Fuse blew immediately again, and the new dimmer switch let out the magical smoke again. WTF!

I've just been dealing with the gauge lights not working for a couple months, but it's pretty annoying not knowing my speed at night..

Any ideas?! Anyone have this happen? I put in an aftermarket head unit, but the fuse blew like two months after I did that so I don't think that's the problem..

Any ideas would be a great help! Thanks guys

[Al 96 Ram Air T/A]

A fuse can blow for one of two reasons. Too much amperage or too much voltage.

What voltage are you seeing? I'm wondering if perhaps the alternator/battery are putting out the correct voltage? Should be about 14 or so (to properly charge the battery). With the car not running, you should see 12 - 13 volts.

If you're seeing much more, you may have found the problem.

[JeffM]

Hmmm.. I guess I'll check.. I'm a dummy with electronics though. I do have a digital multimeter - do I just put the probes on the battery while the car is running and read it? Sorry if it's a dumb Q - I was never good with electrical crap.

thanks

[Al 96 Ram Air T/A]

Well, that'll at least tell you what the alternator is putting out. When the car is off, the voltage will drop, showing what the battery is putting out.

After that, check the power going into the dimmer circuit. You can check it at the fuse (red probe in the side closest to the battery, the black ground to ground/metal body part). You can also check the radio circuit, since that's giving you problems too.

You can't hurt anything with the multimeter. It can tell you alot about what's going on. The smoking dimmer tells me it's getting the wrong voltage. (smoke means it's burning up). A dimmer is simply a resistor. The more resistance, the dimmer the light because the voltage drops and the dimmer bleeds it off as heat.

[Trash man]

get a diagram for the dash on ur car. remove the switch and see how many amps are gettin drawn, sounds like u have a short. amps blow fuses, volts dont blow anything, remember u can get hit by lighting and be ok but if u get 1 amp from a wire, u could die

[Al 96 Ram Air T/A]

Now that I have time to think about it some more, Trash Man is right. I can't see the voltage problem being relevant. The increase in voltage would have to be huge, and the alternator can't produce enough.


I don't think the two issues are relevant. Sounds more and more like you have a short drawing too many amps. Trace the wire back...look for torn insulation. If possible measure the amps on the circuit.

[RangerBob]

Basic electronics. A poor connection can be resistive, decreasing voltage. Make sure that all connections are clean and bright metal.

I corrected my mistake Fred

[Injuneer]

A poor connection will incerease voltage loss. But it can't create volts that don't exist. At no point should the voltage in the circuit exceed the voltage available from the alternator. While current flow is proportional to voltage, it would take a large increase in the alternator operating voltage to increase the current through the circuits, as Al has already discoverd. Its worth checking the system voltage, just to rule out that possibility.

On the other hand, the power consumed in the dimmer rheostat (and being converted to heat by the variable resistor) is equal to current squared X resistance. Increase the current through the dimmer rheostat due to a short in the panel by 42%, and the heat generated by the dimmer doubles = smoke. I suspect, as others, that there is a short somewhere between the dimmer switch and the components in the cluster.

[JeffM]

Ok, it's gone from bad to worse.

Took the car out today for a drive because it was nice out. Everything was fine, till later on in the night. I came out to the car and turned it on, and now the radio does not work, and all the gauges are zero'd out... Jesus.

The only gauges that work are the oil pressure, volts, and I think the fuel.

Oh, and the trunk release mech. is not getting power either

This sucks. I hate electrical probs. All fuses are good - even replaced the radio and gauges with new ones and still no worky.

I just checked the battery with the car off and it was at 12.2v. While running it's 13.96v.

[Al 96 Ram Air T/A]

I feel your pain.

I had a similar problem on my 86 Z24. After almost a year, it turned out to be a broken wire inside the door that was intermittently shorting to the body.

Take a look at the wire running from the fused circuit that keeps blowing. Anywhere it passes through a cavity, it may have rubbed through and is shorting, causes a voltage spike which is affecting other circuits. Check any bundles that are taped together. If it passes through, over, around any metal body parts, you may have found your answer.

Takes time..I know, and it stinks!

[Trash man]

dont think its the dash unit itself do ya? i kno chrysler minivans do that