new battery, low volts. Need help

[bdmstang]

My friend has a 92 Explorer and recently his voltmeter was showing around 10 volts. So he replaced the battery and the volts still read low and over 3k rpm, the volts spike to around 18 volts. Does anyone know why this might be happening? The alternator seems to be fine.

 

[Robb]

I would say regulator is shot in alternator. When engine is off, do you still have only 12V? When running, you should have a little over 13V at idle and probably a little over 14V at high RPM.
If less than 12V when off, sounds like bad battery.
If charging spikes to 18V, regulator is bad.
One or maybe both,
Robb

 

[aldive]

Have you checked the battery and alternator output with a good voltmeter, not the cars ?

 

[wpurple]

Have to agree with AL, you also didn't mention if there was problems with the vehicle. What opt'ed you to measure the voltage? Those readings sound incorrect. If the battery voltage is 10V it sounds like there is a heavy load on it and not charging. Should be 12V when the truck is not running and 13.8 or so running.

Try the voltmeter on a known good vehicle, also, have the original battery tested.

-K

 

[UTexplorer51]

the voltage regulator is out. take it to autozone and they will test the altenator for free while its on the vehicle. be careful because it could fry the battery if it is overcharging.

brian