Voltage meter in instrument panel reads above 16V

Hi everyone, 1999 996 manual transmission. The voltmeter in the instrument cluster reads normal when I turn the car on (before the engine starts.) Around 12V. Start up the car, and it behaves normally (around 14V) for a while. Then it 'floats' up to past 16V. After driving, shut the car off. Turn the car on (before the engine starts) and voltmeter still reads past 16V (off scale 'high.') I tested the cigarette lighter and it reads around 13.7 volts while the car is running. I tested the jump post and it reads around 13.9 volts while the car is running. Could this be a bad voltmeter, a bad connection, a bad voltage regulator, a bad battery? The car has sat for two weeks while I was away for a business trip.

Test the cigarette lighter with the car not running. Betting it will read 12v, and the gauge is whacked. The ~14 reading while it's running indicates the voltage regulator is working fine...

Yep. cigarette lighter, car not running: 12.1V. Does this mean I need to buy a new voltmeter?

Quotes source post: 12512520

What's the reading from the lighter when the car is running? If it is around 14, your gauge is bad. If it reads the same as your gauge, then your voltage regulator on the alternator is bad. Pray that the reading on the lighter matches the gauge. The voltage regulator is MUCH cheaper to replace as the gauge cluster is a single unit. You can get a used cluster around $500, but you'll be stuck with the donor car's mileage, option, and VIN (there is a way to fix that, but it's not for the feint of heart or those without top notch soldering skills). The last I checked a new cluster was $2500 and I was told there were only 5 left in the US at that time (no idea if that was really true or if it represented no more were going to be available).

Car off Cigarette lighter: 12.1V Meter (in instrument cluster) >16V Car on Cigarette lighter 13.7V Jump post 13.9V Meter (in instrument cluster) > 16V I think it is a bad cluster. The car is 16 years old, so one bad gauge is not such a bad thing. Two questions: 1) Am I correct in assuming that if the jump post is reading ~14V that at least the ECU and other electronic goodies will not cook as I drive the car? 2) Have any of you used North Hollywood Speedometer or vdorepair?

1) The voltage indicated by your meter - ~14 - is optimal when the car is on and will not harm the electronics. I agree with your diagnosis that the gauge is borked. 2) No, but I have seen others recommend NHS.

Bummer, sorry. I talked to vdorepair when our cluster snowflaked (but it fixed itself? Never heard of that, but nary a bad pixel now). I liked them, but they were upfront that when you start trying to repair the clusters there is a good chance you'll mess up something else (usually the LCDs). So you have to be prepared that additional costs may come up.

Yeah, I was going to make a similar comment - seems like a decent number of people who mess with the gauge cluster wind up screwing the pooch to a varying degree. If you're worried about having access to the actual voltage value, the Torque app plus a BT OBD-II dongle will give you the data for $20ish bucks, and you won't risk wrecking the cluster. You'd also have access to the actual values for other things (coolant temp) rather than having to rely on the notoriously inaccurate temp gauge... You could also wire up a discreet voltage gauge somewhere else on the dash, but that might be a bit ghetto.