Confused??? I replaced the alternator but not the regulator.
I the installed a voltmeter under dash. First read 12 volts, started engine went to 14 and needle was jumpy but not bad, then next time I started the car pegged at 18 volts and stays there even when disconnected. I took it back and installed another and same thing.
Obviously a problem..
does this make any sense to anyone??
My thanks,
Don

How did you hook up the voltmeter? It should be hooked up to a switched power source (at the fuse block) and a good ground (preferably the battery). I your car has poor ground and you hook the voltmeter to the same ground, this can cause transient current to flow through the voltmeter, frying the winding. So, before trying this again, make sure that your body, frame, and engine grounds straps are not corroded.

Hope this helps.

Hello,
Thanks, I will try another one. I did ground it to the voltmeter. I will next run a wire from the battery when I try another one.
Thanks a lot,
Don

How did you hook up the voltmeter? It should be hooked up to a switched power source (at the fuse block) and a good ground (preferably the battery). I your car has poor ground and you hook the voltmeter to the same ground, this can cause transient current to flow through the voltmeter, frying the winding. So, before trying this again, make sure that your body, frame, and engine grounds straps are not corroded.

Hope this helps.

A voltmeter is a meter movement in series with a large resistor that limits the current through the meter. Having a poor ground will increase the series resistance and cause the meter to read lower than normal.
There's no need to use a switched power source, the current draw is in the order of 1 milliamp, a negligible amount. It woult take several years to drain the average car battery.
When you installed the replacement meter, did it read 12v before you started the engine?

Hello,
Yes both meters read 12 volts before starting the engine. After starting the needle was wiggling at about 14 volts,then all of a sudden went to 18volts and pegged forever on or off.

thanks, don