strange alternator

[KParsons]

AH64ID you are the man. i swapped and it is back to 14.5 volts on both, and the dash as well. i still not clear how it works ,but it does. thank you all.k

 

[AH64ID]

AH64ID you are the man. i swapped and it is back to 14.5 volts on both, and the dash as well. i still not clear how it works ,but it does. thank you all.k

Hopefully it was just a loose connection. If not, the issue will return when a the batteries discharge some.

 

[MMcCallie]

This is typical of AGM batteries. I have been through dozens from AutoZone that read differently from one to the other wired in the factory 12v parallel arrangement. I suggest keeping your stronger battery on the side wired to the starter.

 

[MichaelOverfield]

I second the comment that new doesn't mean OK. I had a bad Odyssey AGM that did not last a year, and when it died for good, it killed the other battery. The procedure to charge a deeply discharged AGM requires a really high amperage charge, that did not work, but it did make one battery start to leak, which is something an AGM is not supposed to be able to do. In my case both batteries were replaced under warranty, at no cost to me, but it was still quite the hassle.

 

[MMcCallie]

I had nothing but problems with Odyssey batteries and I've even had Optima batteries leak. XS Power is what I plan to install when I rebuild my charging system, likely with a paid of Group 31s. Johnson Controls manufactures almost every parts store brand so finding better than mediocre quality is challenging.

 

[3rdGenGuy]

Cooked Primary Field Control circuit in your ECM from factory ground issue. Do an external voltage regulator, put a load ballast in the hot wire from ECM to at least not have a dead dash needle(not accurate just making ECM think it’s doing something) and bypass battery sensor under driver’s side battery bucket. Or a repaired ECM or new. As I recall Mopar1974 on his site listed a fix for that bad ECM charging circuit ground.

 

[AH64ID]

Cooked Primary Field Control circuit in your ECM from factory ground issue. Do an external voltage regulator, put a load ballast in the hot wire from ECM to at least not have a dead dash needle(not accurate just making ECM think it’s doing something) and bypass battery sensor under driver’s side battery bucket. Or a repaired ECM or new. As I recall Mopar1974 on his site listed a fix for that bad ECM charging circuit ground.

Do not do an external voltage regulator.. that’s a bandaid for other issues. Both batteries act as one, if they aren’t then the issue isn’t related to the ECM or alternator.

 

[3rdGenGuy]

That’s incorrect sir. ECM reads off driver’s side battery. Alternator charges on passengers side battery. Obviously this is a temporary fix to get you down the road. A ground repair and repaired or new ECM is the proper fix, obviously. This could also be ICM but for this issue I doubt it. If you bypass primary field circuit after checking for voltage spikes and that is indeed what you have it’s a driveable vehicle after this fix.

 

[3rdGenGuy]

Also the battery temp sensor won’t cause an overcharge.... it just varies the charging rate based on temp.

 

[AH64ID]

ECM reads off driver’s side battery. Alternator charges on passengers side battery.

Correct... and if the voltage is different between those two batteries, if the batteries are both good, then the issue is the connection between the two and nothing else. A bad ECM voltage regulator cannot cause a disparity in charge rates in a properly functioning system, i.e. the crossover cable/connections/grounds. The way the 12V system is setup on these trucks makes it 1 large 12V bank, not 2 separate banks.

An external regulator will not fix the issue, it may mask it but why spend money on the wrong parts?

 

[3rdGenGuy]

Hmmm...well let me check on that then. I do understand the charging system but my crossover seems fine, at least on both ends. I’m just telling you guys what I did to fix the issue with my truck. ICM needs replaced though, and ECM most likely