gm91vette

I have used this forum before with great success, so I'm hoping to get some help with this electrical problem. Car is a 1991 and is completely stock. The battery is not always being charged by the alternator (input voltage measured at the battery terminals with the engine running is 11.2v). Alternator is new, but I suspected it could be bad. Removed alternator and had it checked at parts supplier and it tested OK (14.3v
output). Replaced it on car and it starting charging battery (14.3v at battery terminals. Drove car for a week and problem returned (back to 11.2v). Checked with scan tool and no codes were shown. Hoping you folks have some suggestions. Thanks.

Joe C

clean and double check all your battery connections, as well as alternator connections. make sure you have a good ground to the engine block. if need to, run a temp ground - battery to engine. since the alternator checks OK, give the battery a check. time to dig out the FSM.

edit: need to ask - original alternator? OE should be P/N 1101601 (105A).

Izzy Dizzy

You didn't mention the age of the battery. If it's over three years it could be suspect. You might want to get it load tested in any event. Carefully check the side terminals. Sometimes corrosion will build up between the bolt head and the contact point. You can clean them with a mixture of baking soda and warm water. Just remember to rinse them with plain water when finished.