Hello, I wanted to share my experiences with an intermittent battery warning light on a 2012 Town and Country Touring with a 3.6 VVT Pentastar engine. As this took me quite some time to figure out and was a huge pain in the @$$!

I recently started experiencing an intermittent battery warning light with no DTC codes. Some days it would come on and other days not at all! I did several checks to confirm the alternator, cables and grounds were good (tests below) and all seemed to check out.

Alternator Tests:
Alternator B+ to Batt (+) Term = 0.13 Vdc
Alternator Housing to Batt (+) Terminal = 14.14 Vdc
Alternator Housing to Batt (-) = 0.017 - 0.025 Vdc
Alternator B+ to Alternator Housing = 0.025 - 0.030 Vac (Note this is AC voltage to check for bad diodes!)
Alternator B+ to Alternator Housing = 14.3 Vdc

After those tests confirmed my alternator and cables were okay. I started monitoring battery voltage while driving the vehicle using a scan tool. The scan tool pictures below show what was happening when the battery warning light would come on . It shows the alternator voltage dropping rapidly then shooting back up rapidly. My guess was the PCM detecting low voltage and trying to compensate for the rapid drop in charge voltage.


My first thought was a failing PCM module, bad/loose harness connection or damaged wire. But considering the alternator test results above, that didn't seem like the issue. Then looking at the graph closer, it shows voltage dropping to key-off battery voltage (~12.8 Vdc) or the alternator completely dropping out. Thinking it could be a slipping belt, I replaced the belt and tensioner/pulley, but the battery warning light came up again.

As a shot in the dark, I decided to replace the alternator (as I have had issues with them failing in the past on this vehicle). After I removed the old alternator, I noticed that the alternator clutch pulley had more slip to it than the remanufactured unit I purchased. A few days after I replaced the alternator, I have not experienced the intermittent battery warning light any more and it appears the charge voltage has increased from ~13.9 Vdc to ~14.1 Vdc while driving. Which could possibly further explain a loose or slipping clutch pulley.

I plan to tear the old alternator apart and inspect everything, but I'm leaning towards this issue was caused by a worn or slipping alternator pulley clutch. From what I can gather, the clutch was slipping for a short time and reducing or freewheeling the alternator rotor causing voltage to drop. Then the clutch would re-engage, PCM would detect low voltage and pump current to the alternator field to boost output voltage.

When I read the service manual, a low voltage DTC will be generated if voltage is less than 11.5 Vdc and a high voltage DTC will post if voltage is higher than 16 Vdc. Based on the scantool readings, the vehicle never got to those voltage limits. So that would explain why a DTC code was never posted. What confused me is I couldn't find any info about this battery warning indicator illuminating due to the issue I observed. This appears to be another detection method done by the PCM for fluctuating charge voltage which does not generate a DTC code but still generates a battery light warning. Can anyone comment on that?

Whew...sorry for the long story, but I hope this explanation and diagnosis helps some people in the future. Intermittent issues are the worst! I was planning on shotgunning the alternator and PCM module together. But in my case, appears it was a simple worn out alternator clutch pulley. This should apply to multiple Chrysler products as they likely have similar alternators for multiple vehicle.

Cheers!