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Looking for some guidance. When I pull my light switch on my 88 IROC Z my lights do come on front and back but my dash lights are all screwy. Only my odometer light partially works and my 'brights' indicator is one (though the headlights are only on low. Also both my turnsignal indicators are both on, but my oil pressure indicator, water temp sender, fuel gauge, and charging indicator do not work (dropped to the bottom of their guage) Yet if I turn the inside dimmer switch nearly completely off all my guages and indicators work fine??? What?? the IROC runs fine but I am worried that all the lights will just stop working at all if I don't find the problem.
Anyone else run into this? Seems to me that it is my headlight switch, can anyone shed some insight on this quirky problem I have? Thanks in advance

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OrangeBird

iTrader: (1)

Your headlight switch it likely fine , and not the prime suspect here . Somewhere in the circuit to your instrument cluster , you have lost the ground connection and your lights are backfeeding through other lighting circuits to find their return path instead . This is why the inside dimmer switch changes things , you are altering the way the light find their return since the normal return has been lost .

Now , thing is , WHERE has the lost ground went ? Well , a good start would be to establish exactly when and how the problem first started . I saw a thread recently where it was possible that a recent radio install may have involved a miswiring to the instrument light circuit . In your case , with a missing ground , I'd again ask , did any dash/radio work happen recently to the car ? I've seen several instances of folks messing with , and messing UP , the dashboard's ground connection when installing aftermarket radios and such (aftermarket gauges/tachometers and such are also suspect) so any recent work would bear looking into . Next , Id pull the instrument cluster out of the dash which is many small bolts but connects to two plugs hard mounted into the dashboard . of course , there are many connections at those two plugs and at least one if not more are supposed to be grounded . using the car's wiring diagram I would determine which of the plug's terminals were supposed to be ground and using a meter I'd determine if the required ground was present . If I found the wiring to be OK , I'd then examine the foil traces on the back of the instrument cluster for burnt/open sections , and by then the problem will have revealed itself as I'd have examined the entire cluster ground circuit at that point ...

fivestar

Orangebird thanks for the reply. No dash, radio or any other changes or dealings at all. Radio installed 8/9 years ago and the only thing I have done in the dash area was two years ago I removed it to fix a broken trip odometer but have had no trouble and none of the odometer fix was electrical, by the way I did replace the dash bulbs while I was there since the bulbs were getting on near twenty five years old.... The problem appeared right about two weeks ago...Looks like I will be taking out the dash/instarment cluster and checking the electrical connections and the back circuit board. I will keep you up to date on what I find.
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patrickz1985tgc

Ive had a similar problem. I changed my headlight switch because i thought that would turn my cluster backlighting off but that didn't work. There was an orange wire on the harness that had been twisted on the yellow 12v radio wire. After i noticed that i took the orange wire off now my taillights and instrument cluster lights don't work now

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Well I got lucky, Been dreading going in to figure out why my dash lights were so wacky...Found out that one of my backup bulbs was out and once I changed it out the dash lights are all up and working. While I was there I changed out all the rear bulbs and found they were all original since the Iroc was built back in 1988 (had all the yellowish thick bulb grease) I figured since I had all the interior panels out and it cost less than $20 to replace them all. So check to insure all your bulbs are good before you tear into the wiring or removing the dash...

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Woohoo! Seems that changing the broken rear bulb was simply not the problem on my 88 Iroc convertible. Discovered about a week later my dash lights gave out again.... So I played/jiggled around the headlight switch and found that sometimes the dash lights would work. So today I had a 60 degree and sunny day out and tore into it.. Also found that the contacts on the back of the dash had some light turqoise corrosion as did the headlight switch. Replaced the switch and cleaned up the contacts both on the back of the dash and at the connections (spread a bit of electric contact grease on all the contacts too) and now everything is working great! Sometimes it is the simple things and only $20 for the switch!

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