Electric

[MarieC27]

Hi, I have a 2011 Jeep Liberty 3.7L V6. I’ve replaced the alternator twice and also replaced the battery, but the charging system still isn’t charging properly. I checked the fuses and relays and everything seems to be good. Both alternators tested good as well.
I tested the two wires at the alternator connector. The red/gray wire has the correct voltage, but the brown/dark green wire has lower voltage. From what I understand, that wire is the field control wire that goes to the PCM. At this point, I’m not sure if I have a problem with the wiring harness or if the PCM/voltage regulator is the issue. Has anyone had this problem on a 2011 Liberty 3.7L and know what I should do?

 

[Shaggy]

Hi, I have a 2011 Jeep Liberty 3.7L V6. I’ve replaced the alternator twice and also replaced the battery, but the charging system still isn’t charging properly. I checked the fuses and relays and everything seems to be good. Both alternators tested good as well.
I tested the two wires at the alternator connector. The red/gray wire has the correct voltage, but the brown/dark green wire has lower voltage. From what I understand, that wire is the field control wire that goes to the PCM. At this point, I’m not sure if I have a problem with the wiring harness or if the PCM/voltage regulator is the issue. Has anyone had this problem on a 2011 Liberty 3.7L and know what I should do?

Lower voltage on that field wire can actually be normal, the PCM pulses it on and off fast and a meter just averages it out low. Before blaming the PCM I'd clean and check the grounds, engine to body and battery to fender, then ohm that wire from the PCM connector to the alternator plug. If the wire and grounds check good, the field driver in the PCM is the usual culprit on these. What's the battery voltage at idle with it running?

 

[MarieC27]

Lower voltage on that field wire can actually be normal, the PCM pulses it on and off fast and a meter just averages it out low. Before blaming the PCM I'd clean and check the grounds, engine to body and battery to fender, then ohm that wire from the PCM connector to the alternator plug. If the wire and grounds check good, the field driver in the PCM is the usual culprit on these. What's the battery voltage at idle with it running?

Without running the battery is 12.2V and running is 11.8V I checked the ground under the battery and the grounds that are visible for me are good I personally clean them.

 

[JeepinSteve]

As Shaggy mentioned above, first check all of your ground connections. If you you believe it's the pcm you can use an external voltage regulator. They make some that you can adjust the voltage output. There are many videos on Youtube explaining how to bypass the pcm with an external voltage regulator. It's very easy and they are relatively cheap.