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roy
roy, import/domestic specialest
Category: Dodge
Satisfied Customers: 6173
Experience:  ASE master tech for 40 years
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I have a 2005 ram 3500 that is overcharging the batteries at

Customer Question

I have a 2005 ram 3500 that is overcharging the batteries at 16.7 volts, and spiking higher. I have replaced all battery cables, the BTS, the Alternator, and the ECM. I have had both batteries tested, and they tested good. I also shot the wires from the BTS to the ECM to see if there was any type of short, but it showed very low resistance.
Submitted: 11 months ago.
Category: Dodge
Expert:  roy replied 11 months ago.

hello, my name is ***** ***** I will be glad to assist you. please allow me a couple of minutes to gather some basic info.

Roy

Expert:  roy replied 11 months ago.

good afternoon my name is ***** ***** I will assist

the pcm, was it new or used. did you have it flashed to your truck??

what brand alternator???

Roy

Customer: replied 11 months ago.
The ECM is remanned, and it was flashed to the truck. I don't remember the manufacturer of the alternator, but I can find out once I get home.
Expert:  roy replied 11 months ago.

ok, thanks.

I attached a wire diagram for you to view

can you check the voltage on both little wires that go to the pcm while running???

Roy

Customer: replied 11 months ago.
Which wire number on the diagram are you referencing?
Expert:  roy replied 11 months ago.

1 and 2

Roy

Customer: replied 11 months ago.
Roger that, it'll be a couple of hours before I can get it, but it'll be tonight
Expert:  roy replied 11 months ago.

I will be here

Customer: replied 11 months ago.
Ok, so one of the wires is bouncing between 2.5 and about 4.7, the other is .03-.04
Expert:  roy replied 11 months ago.

ok, so the black wire has what voltage???

Customer: replied 11 months ago.
03
Customer: replied 11 months ago.
Does that not seem right?
Expert:  roy replied 11 months ago.

no, that means it is grounded. but you should have voltage at the other wire.

it concerns me that the pcm is the issue. I have no faith in re man units. the fact that it is charging too much tells me the alt is working but the regulator is the failure. that is part of the pcm.

Roy

Customer: replied 11 months ago.
What would be the odds that a different ECM would perform the exact same way as the old one?
Expert:  roy replied 11 months ago.

they both could have had the same issue. remember, the replacement is not new, it is re furbed

Customer: replied 11 months ago.
I'll contact them tomorrow and see about getting another one
Expert:  roy replied 11 months ago.

ok sounds good

Customer: replied 11 months ago.
I was able to get a new ECM, same result... I talked to an engineer over at Mopar, and he was able to get me some troubleshooting charts that helped me check through some certain wires for continuity, shorts, and resistance. All to no avail. I wasn't able to get ahold of him again, but now I'm wondering if it could be something in my PDC, or the FCM
Expert:  roy replied 11 months ago.

according to our checks, you had all the needed voltages. that would eliminate the pdc and the fcm.

Roy

Customer: replied 11 months ago.
Well crap, maybe I have an intermittent short that only shorts while it's rattling around
Expert:  roy replied 11 months ago.

it is possible. do the wigle test while running and see if the charge rate goes up