Every time you turn on the dimmable dash lights the voltage gauge and gas gauge drop to 0 or pretty close. I just changed the alternator and the battery is less than a year old. When the voltage gauge drops and i come to a stop the voltage regulator clicks. The alternator recently went out i think because of the stereo that was improperly installed by the previous owner and grounded out
My car has 239000 miles.
My car has an automatic transmission.
Definitely check that the stereo was installed properly. If you can’t find a wiring diagram online, try a local stereo installer. They might be able to help you out. GM products, particularly in the 80’s, were prone to gauge issues. I had one. Typically is was due to a faulty ground or the "gauge amplifier" that is part of the instrument cluster internals. Mine was an 85 Olds Cutlass 442 that the tach and oil pressure gauges had a mind of their own. The tach would be reading correctly, then hit a bump or turn the lights on and it was reading double the actual rpms. If the problem persists after verifying that the stereo was wired properly, loosen and reconnect the instrument cluster and check the wiring to it. If that does not correct the issue, it may very well need a new instrument cluster.
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