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Dash Battery Light

52K views 13 replies 5 participants last post by  slacktide 
#1 ·
Past several weeks i've had the charging system warning light on the dash. Last Wednesday Jeep wouldn't start. Checked the factory battery and it was bone dry. Topped it off with some water and jumped and rolled into work. During lunch picked up the only 34 series battery the Exchange had in stock. Installed and no warning light.

All was good on the world again.

Drove home and the damn light came on again a few miles from the house. Pulled into the drive and popped the hood to put an eyeball on the ground strap and the alternator was on fire!!! Cursed a few times and started calling around to find a new alternator. No one, not pepboys, napa, advanced auto, carquest, autozone, had them available yet from the supplier. A 2007 was just to new. The dealer would have to order it. Would take about a week and run $275. The Exchange could have it rebuilt by a local shop in one day for $140 so I went that route. Dropped it off the alternator on Thursday morning, picked up that afternoon, and installed it that evening.

Fired right up, no warning light. All was good with the world once again.

Drove to work Friday. Around town al weekend, to work again on Monday and this morning. The on the way home this afternoon the damn light comes back on!!! WTF!

So I've checked all the wires and the negative cable to ground. All wires appear to be good with solid connections. The battery and alternator shouldn't be the issue now that they have been replaced. What else should I be looking for?
 
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#3 · (Edited)
You have some serious chit going on there.
Did you check for fault codes? The charging system is monitored and will set codes.

Having the alternator rebuilt will not include the voltage regulator, as that is in the Powertrain Control Module. If it is bad, the PCM needs to be replaced.

Check for codes.
Check the charging voltage with a volt meter (engine running about 1,000 rpm, don't stand in line with the belt).

You may have to have the dealer hook up their scan tool to see what the charging system is doing.
 
#8 ·
Dropped the JK off at the dealer this morning and picked her up at lunch. Ser ice writer said the negative battery cable was loose and that was the issue. That threw me for a loop cause I knew I tightened it good last night.

So pullout of the parking lot and Ding, on comes the light. Back to the dealership it went. After work picked up again, and the service writer says they couldn't reproduce the light and everything looks fine.

Start the jeep in the parking lot and there's the F'n light! Showed the service writer and his response was "dunno, tech said all everything checked out.".

Guess I'll try another dealership if the jeep doesn't burn to the ground before I can get it in. :bawling:
 
#9 ·
this happened to me on my old Ranger (I know its not a Jeep, but may be related), and turned out the voltage regulator was shot, I also noticed that the light came on under heavy acceleration

the dealership replaced the whole alternator and problem solved
 
#12 ·
P0622-GENERATOR FIELD CONTROL CIRCUIT

Set Condition:
When the PCM tries to regulate the generator field with no result during monitoring. One Trip Fault. Three good trips to turn off the MIL.


Possible Causes

(K125) GEN FIELD CONTROL CIRCUIT SHORTED TO VOLTAGE

(K125) GEN FIELD CONTROL CIRCUIT OPEN

(K125) GEN FIELD CONTROL CIRCUIT SHORTED TO GROUND

GENERATOR

POWERTRAIN CONTROL MODULE (PCM)
 
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