Questions and Answers

Chevy C1500 Volt Fluctuation Q. I have a 1993 Chevy C1500 Ext Cab with the 5.0 liter engine, automatic transmission, A/C, and the gauge cluster without the tachometer. I am experiencing a problem with the volt gauge, where it will sit at 14 volts, then drop down to 12.5 to 13.5 volts. When it drops, my voltage at the battery does not drop, and I had a friend bring a scanner over, and the computer was reading the battery voltage accurately.

The problem is, the idle will pull down until it almost stalls, then rev up a bit until it pulls down again. It doesn't usually stall, but has done on cold days. If the gauge stays at 14 volts, the idle is fine. I replaced the 02 sensor, tried another IAC, but all else seems fine according to the scanner.

I don't understand how the computer can read accurately, and the gauge can be wrong. If it was the cluster, why would it effect the idle? I'm baffled!

Rob

A. Can't explain the idle fluctuation but you may have bad connection to the cluster. you could take it out and take a reading on the circuit that is for the voltmeter. It's a start. A shorted computer solenoid could pull down voltage and make idle surge. Dumb question but did you take off both battery cables to make sure they are CLEAN? They can look good from outside but when removed can be full of white corrosion, very common. Also remove the engine ground and clean it good; and any other grounds you can find. Especially the wires at the thermostat housing