The other day while driving my car the lights started to dim and the gages went out. I was still driving and found out the altanater was bad. I had just put a new battery in too. So my buddy put a new altanater in we charged the battery. I started to drive and in about 2-3 minutes the same thing happened! Any ideas?
I drive a 1999 Grand Am SE 4 cylinder.
Use a digital multimeter across battery posts, everything off. The generic spec for a full charge is around 12.6 volts. Then start the vehicle, take second reading across battery posts, the second reading shouls be high than the first if alternator is charging. You have to test when problem is ongoing. Also, check voltage reading at alternator bat terminal, engine running, If that reading is higher the the reading at the battery, engine running, something wrong with that wiring circuit, maybe fusible link?
Check for charging system trouble codes, manufacturer specific, PO codes probably won't help.