volt guage in cluster reads off the charts

working on a buddy's car, its a 94 z28 that he picked up for 1500.00. problem is its seems to be one big can of worms, its just one problem after another, it looks like it was demodded and sold off.

we seemed to have fixed most of the issues but one that it came in with and i havent looked at was the volt meter in the cluster, reads full sweep past 18v, like its connected backwards or something. we used the volt meter on the battery it reads just under 14v so its charging normal just not reading right. any help or advice would be appreciated before i dig into it.

Does it have a gauge overlay? The needle just might be off from sloppy work.

no overlay, when off the needle drops down to where it should be.

anyone?

Wiring or gauge is about all it could be.

Put a digital gauge on the accessory power port and see if the numbers match up.

If the gauge reads high, but the voltage is actually fine, just make a mental note and deal with it.

If it's under 18 volts, don't worry about it. It's very common for GM alternators to charge at and above 16 volts, and the vehicle's electrical system can handle it just fine. If your alternator is actually putting out like 20 volts or something, get a new alternator (the factory alternator includes a built-in voltage regulator) and hope that it's better. :)

ill check the wiring on the alternator, but the guage seems fine because when its off it drops to normal off position. when you turn the car on it just reads off the charts like well past 18. kinda like its reversed or something. we hooked up the multimeter to the battery and its charging at just under 14 so its working fine just reading wrong.

checked the wiring on the alternator, from what i believe the red slim wire is the read for cluster. if it is then when i removed it the cluster reading did not change, am i missing something here?

jakerobb, where is the accesory power port?

checked the wiring on the alternator, from what i believe the red slim wire is the read for cluster. if it is then when i removed it the cluster reading did not change, am i missing something here?

jakerobb, where is the accesory power port?

The little wire from the alt goes to the gauge cluster, but not directly to the volt gauge. Could be something wrong with the cluster, I suppose.

Your gauges fuse should show the same voltage as the volt gauge.

jakerobb, where is the accesory power port?

Also known as the cigarette lighter. :)