Alternator and battery replaced, battery draining?

KOIOS1031

MEMBER
2016 JEEP PATRIOT
2.0L
4 CYL
2WD
AUTOMATIC
120,000 MILES

A few weeks ago, I was driving down the road and all the dash lights came on. Weird. Then the radio turned off. The car shut off. I drove it to a gas station and changed the alternator on it. The car didn't start. The battery was drained. Okay. Charged the battery and the car was fine for about 20 miles, and everything started up again in the same manner. I thought that it was a bad replacement alternator. I replaced the replacement, recharged the battery again, and was on my way. For about 20 miles. Then it all happened again. The battery is only about 2 months old and has been tested. Before that, I did have to jump the car more than a few times, I admit. I've checked the lines from the battery to the alternator, from the battery to the TIPM, checked any and all fuses I could. The battery is dying again. The PCM/ECM does have the voltage regulator and such. There's no check engine light other than the battery light. Any ideas? My thoughts just go straight to the PCM.

1 Reply

JACOBANDNICKOLAS

MECHANIC
109,867 POSTS

Have you replaced the PCM? If the alternator is good and the battery is good, the regulator integral to the PCM is likely no good and causing this to happen. It isn't a repairable part. Instead, the PCM needs to be replaced.

Try this simple test to confirm the alternator isn't charging. All you need is a voltmeter or a multimeter. Follow the directions in this link and let me know the results:

https://www.2carpros.com/articles/how-to-check-a-car-alternator

If it doesn't show a charge, replace the PCM. (See pics below)

Let me know.

Joe

See pics below.

Images (Click to make bigger)