Q: Old battery tests good. Alternator tested bad but still runs car with a new battery. Shuts off when old battery is put back in.

asked by

James H

on November 18, 2017

My car stalled one day on my way to the store. Seemed like the battery so I keep a spare in the trunk. Switched it out, fired right up got home safe. Next morning it stalled again on me while driving. Same symptoms of a dead battery flickering lights etc. Went and bought a brand new battery put it in and has been running fine for a few days. Got my alternator, starter, and my spare battery tested. Battery-good. starter-good. alternator-bad. Battery dash light still flickers even with the new battery. And hooked up to a voltmeter with BOTH my spare and brand new battery, alternator keeps the charge at around 13-14. Had my spare in after testing the voltage and it wouldn't hold a charge, car stalled after about 3 blocks. But the brand new battery got me the whole way home?? Is this in fact my alternator on its way out or is there another problem to consider. HELP PLEASE

My car has 178000 miles.
My car has an automatic transmission.

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Q: Old battery tests good. Alternator tested bad but still runs car with a new battery. Shuts off when old battery is put back in.

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