Stumped bad: Electrical related; 92 Loyale

[cal_look_zero]

Ok, I goofed up somewhere. None of the stereo shops could locate a wiring harness for me, so I chopped the one off of the stock deck and began looking up/testing wiring. Had it all squared away and got the deck working; except for the fact that the deck and dash lights stayed illuminated since I bridged the 12v constant into the solid red illumination wire. I unsoldered the connection anf left the wire terminated since the red/green illuminated the deck.

 

Now I have no dash lights; inexplicably.

 

I have the entire dash except the gauges pulled apart and have some odd wiring gremlins I can't quite figure out. Firstly; the illumination circuit(s) show infinite resistance to ground when the circuit is off, but 0 resistance when it's on. This in and of itself says that I have an accidental bridge to ground, but I never touched any wiring besides the stereo. However I have the bridged to ground condition with or without the stereo wired in. I looked around for a screw that may have pierced a wire or something of the sort, but I can't find anything.

 

The REALLY odd part, is that none of the gauge lights work except for the ashtray light. I get connectivity between that socket and the rest of the circuit, but it's the only one that lights up. Very confusing since if any of the circuit is grounded out, the ENTIRE circuit should be grounded out.

 

Obvious answers: Yes I checked all of the fuses; both for voltage and for continuity. No I haven't messed with anything besides the stereo wiring. Yes I know what I'm doing electrically. Yes I'm using a high quality (Fluke) multimeter and good leads.

 

I'm one more "midnight drive home from work without gauge lights" away from rigging up some LED illumination so I can see the trivial things; fuel, oil pressure, temp...

[Cougar]

Some of the lighting is on a different circuit than the dash lights so that is why the ash tray light is working. The radio, hazard switch, and cigarette lighter illumination are on a seperate circuit than the other dash lights. They are tied to fuse 9 so you should have power to those lights when the lights are on. The return side of the lights goes to the illumination control module. It controls how much current gets to ground to control the lights. You should be able to turn on the lights by grounding yellow wire to the lights if power is getting to them. If that works then it looks like the illumination control module is bad or there may be a problem with the dimmer control and the wiring between it and the module.

[Meeky Moose]

possible the bulbs have burned themselves out? all at once?

 

i'm more of a mechanical guy vs electrical. pro audio had harnesses for the older wagons last i checked.

[cal_look_zero]

Some of the lighting is on a different circuit than the dash lights so that is why the ash tray light is working. The radio, hazard switch, and cigarette lighter illumination are on a seperate circuit than the other dash lights. They are tied to fuse 9 so you should have power to those lights when the lights are on. The return side of the lights goes to the illumination control module. It controls how much current gets to ground to control the lights. You should be able to turn on the lights by grounding yellow wire to the lights if power is getting to them. If that works then it looks like the illumination control module is bad or there may be a problem with the dimmer control and the wiring between it and the module.

 

Part of my testing involved messing with the dimmer. I stuck my - lead on the black wire, and got 12v across both red wires with no change based on the position of the dimmer.

 

I noticed last night that the gauge surround didn't have any screws in it which leads me to believe that someone may have been in there previously. I'll be going deeper into it tonight; won't be surprised if this whole problem is just coincidental to the stereo wiring.

 

Just going to download a gps speedo for the smart phone in the interim:banghead:

[Cougar]

I'm not sure what black wire you are refering to. Regardless, there should always be 12 volts on the red wires when ever the lights are on and that should never change. The lights are controlled by the return side of the light circuit through the illumination control module. That is where you should see a change in voltage in reference to chassis ground. If the reading is always high it means the illumunation control circuit is open. You can prove it by grounding the yellow return wire of the lights and that should turn the lights on.

Edited October 19, 2011 by Cougar

[cal_look_zero]

I'm not sure what black wire you are refering to. Regardless, there should always be 12 volts on the red wires when ever the lights are on and that should never change. The lights are controlled by the return side of the light circuit through the illumination control module. That is where you should see a change in voltage in reference to chassis ground. If the reading is always high it means the illumunation control circuit is open. You can prove it by grounding the yellow return wire of the lights and that should turn the lights on.

 

Ok, I'll try that tonight. Should help mitigate a lot of unnecessary disassembly and testing.

 

If grounding a yellow gets me dash lights, what would my next step be?

[Cougar]

If bypassing the yellow wire to ground makes the lights work I would suggest you check out the illumination control module for a problem.

[cal_look_zero]

Ok, I think I got it. Grounded the red/green ending at the dimmer switch. I assume (if I'm reading the circuit correctly) that all this will do it eliminate my dimmer? In any case, I have dash lights for now...

[Cougar]

Ok. My info doesn't show a r/g wire for the dimmer control and the only ground wire I see is for the switch.