Voltage fluctuates while driving; "check gauges "

matkal

matkal

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Check gauges light came on and voltage was down to half way between red and 14v. I pulled over, left the engine running and popped the hood, all appears normal. Read a couple threads on here describing the same condition and had the alternator checked at Napa and O'riellys both said it's good. I checked connections at battery, grounds, alt, etc. all were good. Checked voltage across battery and from battery to alt; same readings, which are 12.2 w/eng off and 11.6 running. Pic shows gauge reading. Pulled alt and forgot to check voltage between eng ground and alt. I plan on taking it to an alternator shop and have him test it hoping he will do a more thorough check.

The CEL never lit up.

Thoughts? Should I check voltage between engine ground and alternator?
 
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IMG_0599.jpeg
 
Remove the ECU 32 pin wiring harness connectors and inspect the clips and pins for oxidation.
The ECU controls the alternator charging rate of the battery and to the electronics.
Once you have confirmed the harness connectors condition; you can move on to checking the battery cables internal copper strands for oxidation,
Trace the wiring from the alternator charging stud to the battery and inspect the cables internal copper strands for oxidation.
Remove the cover of the PDC (fuse box in engine compartment); with the engine running check the incoming voltage of the power cable from the alternator to PDC power stud.
There is more testing that can be done, but these tests will provide you with what direction to go .
 
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CharlesHS said:
Remove the ECU 32 pin wiring harness connectors and inspect the clips and pins for oxidation.
The ECU controls the alternator charging rate of the battery and to the electronics.
Once you have confirmed the harness connectors condition; you can move on to checking the battery cables internal copper strands for oxidation,
Trace the wiring from the alternator charging stud to the battery and inspect the cables internal copper strands for oxidation.
Remove the cover of the PDC (fuse box in engine compartment); with the engine running check the incoming voltage of the power cable from the alternator to PDC power stud.
There is more testing that can be done, but these tests will provide you with what direction to go .
Click to expand...

Voltage is 11.53 across all combinations: batt negative to pdc, batt positive and at the alt. Same using firewall ground and engine ground. Gauge reading is the same
 
matkal said:
Voltage is 11.53 across all combinations: batt negative to pdc, batt positive and at the alt. Same using firewall ground and engine ground. Gauge reading is the same
Click to expand...

All of that testing and results were found with the Jeep running ....
I just reread your earlier posts and if the voltage is 11.6 with the engine running, all cables and connections have been tested and the alternator has been tested at two AP stores then the problem is either the ECU charging circuit... or the battery has an intermittent problem.
I think I would have the alternator tested at another AP store just to ensure the findings of the other two stores.
 
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CharlesHS said:
All of that testing and results were found with the Jeep running ....
I just reread your earlier posts and if the voltage is 11.6 with the engine running, all cables and connections have been tested and the alternator has been tested at two AP stores then the problem is either the ECU charging circuit... or the battery has an intermittent problem.
I think I would have the alternator tested at another AP store just to ensure the findings of the other two stores.
Click to expand...

Yes, all tests with engine running. Taking it to a motor/alternator shop tomorrow. I just sent my ECM to wranglerfix trying to diagnose a crank/ no start issue
 
I installed the regulator bypass and I’m pretty sure it’s working as it should. I’ve never really paid much attention to my voltage gauge so I’m not sure how it should read when charging.

Battery was at about 11.5 before bypass surgery. Now it fluctuates between 14.5 and 15.1 with a volt meter, battery is at 12.66 (with engine off) after running/driving for a while.

Does this sound ok?
 
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