HossinatorSS

iTrader: (1)

I'm having some charging issues and am trying to determine if I should start with alternator or battery. With the car off, the batt. voltage is 12.77V with the car running at idle, the voltage across the terminals is 13.5V is this normal? the car doesn't have problems starting, but the voltmeter in the dash will sometimes drop to 8V (with stereo off) and then come back with some revs.

2001NBMZ28

Easiest thing to check is the battery, most parts stores will do a free load test. My experience has been 12.7 at the terminals with car off is normal, running is usually 14.5 just after starting. If it's dropping that low momentarily a new alternator could be in your future - I had to replace mine a few months after my cars voltage gauge started doing that. Posted about it and people said not to worry but it eventually didn't charge and just drained the battery.

RsSean

iTrader: (27)

12.7 off and 14.7 on. Now when the car is put under load the volts will drop. A slugish start with a standard car will cause a drop in voltage.

HossinatorSS

iTrader: (1)

well, maybe it is the alternator, I've been having problems with losing fuel pressure at WOT, thought maybe it was due to voltage drop (not sure how to check voltage at pump) so i'm wondering if maybe the alternator is my problem since it has 96k on it and the battery is between 2-3 yrs old

bb5401000

iTrader: (2)

Check the battery first with a load test. A simple voltage check is not useful. Sulfated plates in the battery will still have 12.6 volts but low current will transfer out of the battery. If it fails the load test, replace the battery, check all the connections and grounds and then do a load test on the alternator to check the alternator. You must have a good battery BEFORE load testing the alternator. If the battery is weak, the alternator cannot generate sufficient current to power the elctrical system.