Question: I see that you have emphisis on Bugs, but maybe you've heard of this particular problem in the Rabbit/cabriolets. I have a 1985 that has got me into a nut-roll. When I bought the car; (I am now the third owner), the speedometer in the guage cluster was the only thing that worked; (in the guage cluster in the dash. The LED display does not work, save the hight beam "blue" LED, when the lights are on high beam. The thing is the tach doesn't work, the gas guage doesn't work and the temperature guage doesn't work. The thing is, all three guages in the center pedestal; (directly in front of the shifter), work fine. Oil pressure, Charging meter and temperature guage.
I have literally pulled the whole dash apart trying to find a bad ground or broken wire to no avail. The really strange thing is that this car has air conditioning installed--that doesn't appear as a factory installed option, more like an after thought.
Can you maybe steer me in the right direction. I have come to the conclusion that all three inoperative guages in the guage cluster must be related. The diodes on the back of the cluster all look fine, as well, the "plastic" in-laid wiring harness [kind of a ribbon cable] on the back of the speedo/guage cluster looks fine under a magnifyer.
Do you have any advice on this electrical problem?
Answer: My advice on this question wasn't very specific. Below my reply, see the excellent solution Chris found. Thanks Chris!
You may need to get a shop manual to know what kind of voltages/resistance to expect on the connections to those gauges and LEDs.
I'd get a good used instrument cluster. If it works, great. If it doesn't then I would try creating a substitue ground, and then after that running a new wire for each effected circuit.
I did recently discover that the dash lights on the '91 Cabriolet (and probably most other VWs) are controlled by a relay. If the relay fails, no lights.
Chris' reply and solution:
It was nice of you to reply. I thought I'd give you the low-down on what was actually the problem for questions that may arrise in the future for VW owners w/ this kind of problem.
Problem: No tach indication/no fuel indication/no eng temp indication at the instrument cluster First, I traced every wire, every ground, every terminal lug end, source to guage
Found: Minor corrosion, several questionable wires where rubbing/chaffing had occurred
Corrective action: Replaced all questionable lugs, wires and terminal ends; verified grounds were clean/clear Second, verified all fuses were clean at the lug ends and that the fuses were physically indeed good Third, at my wits end, pulled the fuse box down and started "oming" wires end to end [using and ohmmeter to verify that the wires conduct] Fourth, frustrated, again, pulled the fuse box down, pulled the relays out to check them.
Found: Relays by the previous owner had been removed/replaced incorrectly; no. "3" was in no. "5's" position, "4" was in "3."
Corrective action: cleaned up the lugs on the relays and placed them in the correct position.
Solution: Everything works! After Action: Even though some bad wires were found and some corrosion was corrected, a whole lot of stress was going on needlessly. For anyone in the future w/ this kind of problem I'd vote common sense.
(1) Check the fuses
(2) Check the relays w/ (against) known good ones
(3) Verify that everything is "where it was supposed to be in the first place," against a stock wiring diagram. If I'd of followed those simple steps above I'd of solved my problem right away and fiddled w/questionable wires later, (under no stress), knowing what my eng. temp was, and how much fuel I had on hand.
Thanks for the help/response,
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