‘83 Voltmeter Questions

[Bob Q]

Just finished up doing the LMC tach conversion in my ‘83 K2500 6.2L. Took it for a ride this evening to double check everything before putting the instrument bezel back on. Tonight, the factory voltmeter starting reading high (15-16 volt range) just before the red zone on the upper end. It’s never read that high and I’ve never had any issues with it up until tonight. I checked the batteries with a multimeter and they were about 12.7 volts with the engine off and about 14.5 volts with it running and the gauge was still reading high. Do you think the voltmeter is going wacky or is there something else that could make it read higher all of a sudden even though the charging system itself seems fine?

Thanks.

[Bob Q]

Anyone have any thoughts on this one?

[Wgesnerjr]

One thing to keep in mind that the accuracy of the stock gauges was not that precise. However if it is reading high after the tach install, I would think that has more to do with it. Since your testing of the battery and alternator showed no issue, I would start with checking the power at the gauge and see if it measures the same as the alternator/battery. if so, I would say the gauge is not accurate. Might also check the grounds at the dash to make sure they are clean. Poor grounds have been known to do weird things.

hope this helps.

[JJH Jimmy]

Did you mess with the resistor on the back of the volt meter? If the resistor is not there the meter will peg.

[Bob Q]

Thanks for the tips. Nah, I didn’t mess with that resistor or anything with the gauge. Just seemed to start reading high all of a sudden. I’ll check the grounds.

[Bob Q]

I checked/cleaned grounds and cleaned connections at the alternator, no change in the gauge reading. Took voltage at the output of the alternator and it's around 14.95-15 volts. Might pull the gauge next.

[Pontiac1976]

If everything check out you can take your Alt in for a test
shop to make sure the regulator is not over charging. If it test good I would think the gauge might be having trouble since the tach up grade. Hum maybe out there but is the tach drawing more power load then it should.

14.95-15 volts.

your #'s seem about right. things to look at how old is the Batt did it de-charge from the time you did the work, are you still running 35AMP none A/c or the 55AMP A/c stock alternator or have you up graded. If you had up graded the alternator and still had some bad connection found some that ATL may read a little higher.

[Bob Q]

Yeah, I’m going to take the alternator into a shop for a test on Monday morning.

Thanks for the tips about checking the batteries. I had kept the batteries on a charger when I was working on it, so I don’t think they got too discharged. The alternator is a 78 amp AC Delco rebuild that’s been in there for a few years.

[hatzie]

If it's a GM gauge you either have a loose calibration resistor on the volt gauge canister or the alternator is really putting out that many volts.

If the gauge is part of the LMC kit I'd lean toward a bad gauge.

[Bob Q]

It’s the original gauge. I took the alternator to a shop and it was putting out 15-15.5 volts, so they put in a new regulator and it’s now at 14.7, but the gauge is still reading high at the same place. I’m going to throw another voltmeter in to see how it reads.
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[Bob Q]

Took the alternator to a shop and it was putting out too much voltage. They said it was actually putting out about 15.5 volts, but should be around 14.7, which it is now after they replaced the regulator. So, I figured this was my whole issue. Nope. I put the alternator in and the voltmeter gauge still read high, just like before. I got a new OEM-style voltmeter and it now reads lower and closer to the actual voltage. Seems like all is good now. Thanks again for all your help.

[LT7A]

Glad you got it worked out. Thanks for posting how you fixed it.