Leaderboard

10V isn't usable, it should be ~12.7 volt, 10 isn't even close to good enough. This means one of the following: 1. The battery is bad. If it never gets above 10V with jumper cables or an external charger then it's bad. Sometimes they can test good and still be bad. That's rare but when it happens they'll show 12.5 volts and then *very quickly* drop to well below that the first time the battery is used for anything electrical, like the first time you bump that key to start the engine. 2. The alternator isn't charging the battery, which means one of the following: a. The harmonic balancer is separating and the alternator isn't spinning fast enough to charge. Post a photo of the face of it or paint/grease mark a line across the entire face and see if the line is separated after getting the engine to turn over with a jumper cable/jump starter. b. Test the alternator - jump start the vehicle and test output voltage at the alternator Okay, I didn't think so but I wanted to be comprehensive - that list is everything it could possibly be if what you have currently described it accurate.