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1993 Mustang LX Conv interior illumination not working

1027 Views 5 Replies 3 Participants Last post by  mg man 75
I have searched several times and haven't found anything that seems similar to my issue. Interior illumination initially worked (instrument cluster lights, heater control panel, gear selector, switch illumination, etc.). Driving the car one evening, my daughter lost all of it. Replaced the headlight switch, replaced the headlight switch plug due to the wiring being fried in a few spots (replacement plug from LMR). I have an extensive background in aviation electronics, so when I spliced in the new harness all wires were matched and spliced with good quality butt connectors. All INDICATOR lights (turn indicators, hi beam, check engine, seat belt, etc.) WORK. What I am missing is illumination!
Is there a common ground somewhere behind the dash for all the lighting? EVERY fuse in the panel has been changed. Right now I have a workaround of a clip-on light to see the instruments, but it is a pain LOL. Haven't tried the dimmer control and when I tried to look for continuity etc on the switch the wiring diagrams weren't very helpful. ANY ideas would be appreciated!
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Is it completely dead? Could be the bulbs or the 12v little chip in the back :/ I just found one at a scrap though since it's too expensive new (I found mine in a 95 mustang, a lot of Ford up until I think 95 had them) I know that when these things go bad the clusters go crazy (mine is causing my rpm needle to jump irratically, they also make lights stop working in the cluster, they make things read wrong ect)... also check the roller type light dimmer on side it needs to be clicked on. Also there's that one big circle fuse that made all my stuff stop working when it died
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Dimmer switch is probably it. Had 4 mustangs and 2 were bad and I had to replace.
From a 93 wiring diagram. From headlight power feed by Brown to the dimmer the if want interior lights comes on, power comes out on Light Blue with red stripe this feeds to fuse panel #13 then out of fuse on Light blue with red again to all the lights.
Should be able to follow that and find problem. Maurice
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Thanks for the tips, mg man 75. I have continuity from the fuse panel to contacts A13 and B11 on the instrument cluster plugs. I have 12 Volts DC at three of the four contacts on the Dimmer Control switch. The wire from the Dimmer Control plug to the fuse panel is good. Tried taking apart the Dimmer Control switch as it seemed to have a lot of corrosion in it. Cleaned it up and it seemed to be providing SOME voltage to the fuse panel, but not sure what it is supposed to be (Min and Max). I'm guessing I will have to break down and find a replacement Dimmer Control in a junkyard :crying:
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If you have mustangs in your junk yard look for other parts also...
Kind of hard to find one good. I tried several before finding a good one. Maurice
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