Hello all, I have a bit of a special-case alternator problem, hoping someone has some info.

I have a 2012 Silverado 1500 w/6.2l. It has a problem with the charging system which dealerships have been unable to sort out; basically the PCM/BCM is always overcharging the battery (constant 15.5v). As a workaround, the PWM control wire from the BCM has been disconnected, allowing the alternator's internal regulator to set charging voltage. The second, sensing wire to the alternator is left in place, otherwise BCM throws codes and lights dash lights. The original alternator is the 145amp DR37. This has worked fine for a good while, but it seems the alternator's internal regulator is getting tired, as voltage has been slowly rising for some time.
I tried replacement with 2 different DR44, 160a alternators (also a stock options on this truck), but--unlike my original DR37--they would not charge at all without the PWM control wire connected.

So, my question is if anyone knows details on this. Do all DR37 alternators have a failsafe default to 13.8v if the control signal is lost, while all DR44 alternators do not? Is there another option, like an AD244 replacement? I don't have a problem putting in a new DR37, they just weren't available locally. But without knowing whether all DR37s have a default failsafe voltage, I don't even know if that will solve it, or if I was just lucky with the alternator I started with.

Long term, I will be hunting for bad grounds, which I suspect are causing the BCM to detect lower voltages than actually exist. Failing that, I will hook up my own PWM generator to control alternator voltage. But in the meantime, I just need an alternator to get me down the road, one that will charge without the BCM's control signal.

Thanks for any input!

 

You might be able to fit a 24SI voltage regulator in your AD alternator.. which would make it into a self-excited "One Wire" unit.
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