Volt meter = 12 volts for a minute then ~9.5

2001 XJ Sport

The nut fell off my battery strap, it shook around and the caps came off 3 of the cells and some acid came out, voltage dropped to 9..."check gauges" light comes on.

Got a nice new battery and terminals, same problem.

I start it up (cold or hot), shows 12 V, run it for 30-60 seconds and then the voltage quickly drops down to ~9,9.5. This is consistent, every time for 2 days now.

Anyone seen this? My wiring looks good. A year ago I was just over 14v but since that time it's slowly dropped to 13.5, until a few nights ago.



I'd rather change an alternator than PCM. Doubt it's a loose wire. I'll check the alternator tomorrow. I wonder if something went bad from running on a 9v battery.

You can try whacking the alternator with a pipe and see if the volts come up. The brushes in the alternator wear out over time. A few people replace the brushes, many replace the entire alternator. If you remove the back cover of the alternator you can remove the brushes and check.

SOLVED! Thank you, I tapped it with a hammer and it went back to normal. Looks like I'm in for new brushes. Next time I would actually use a heavy pipe.