How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask roy Your Own Question
roy
roy, import/domestic specialest
Category: Dodge
Satisfied Customers: 4650
Experience:  ASE master tech for 40 years
3506196
Type Your Dodge Question Here...
roy is online now
A new question is answered every 9 seconds

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: 1 month ago.
Category: Dodge
Expert:  roy replied 1 month 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 1 month 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 1 month 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 1 month 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 1 month ago.
Which wire number on the diagram are you referencing?
Expert:  roy replied 1 month ago.

1 and 2

Roy

Customer: replied 1 month ago.
Roger that, it'll be a couple of hours before I can get it, but it'll be tonight
Expert:  roy replied 1 month ago.

I will be here

Customer: replied 1 month ago.
Ok, so one of the wires is bouncing between 2.5 and about 4.7, the other is .03-.04
Expert:  roy replied 1 month ago.

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

Customer: replied 1 month ago.
03
Customer: replied 1 month ago.
Does that not seem right?
Expert:  roy replied 1 month 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 1 month ago.
What would be the odds that a different ECM would perform the exact same way as the old one?
Expert:  roy replied 1 month ago.

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

Customer: replied 1 month ago.
I'll contact them tomorrow and see about getting another one
Expert:  roy replied 1 month ago.

ok sounds good

Customer: replied 25 days 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 25 days ago.

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

Roy

Customer: replied 25 days ago.
Well crap, maybe I have an intermittent short that only shorts while it's rattling around
Expert:  roy replied 24 days ago.

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