[nthill93]

Hi everyone I have a 2001 Cummins and i am getting a surge in the tranny at 45-55MPH. I have read that this is caused by AC sin waves from the alternator. the thing about my problem is that it only happens when i have the heat on full blast. if i put it on level 2 its fine no issues at all once i turn the heat all the way up it surges.

I am going to load test the batteries and clean the terminals my big question is do i need to change the alternator? If i clean the terminals and grounds and it goes away will there still be a risk of the ac sin waves hurting my ECM? is there anyway to protect my ECM dont want to destroy a 2000$ ECM. I tried to find Mopars tutorial on ac sin wave testing but i cannot seem to find it if anyone knows where i can find that i would greatly appreciate it.

 

[Yankneck696]

With the truck running at idle, check at the B+ terminal on the back of the alternator with a digital volt meter on a 2VAC or lower scale. Anything more than.10 (1/10th) volts AC indicates a bad alternator. It can fry the ECM, PCM & VP44 computer.

Ed

 

[dozer12216]

Mopar1973Man has the writeup on alternator testing. If you fix with grounds and problem goes away, you have fixed it's particular issue. Nufffff said..

 

[bigfish95971]

I figured out years ago that sometimes increased load of the fan or power windows, etc , will exacerbate he AC noise coming from the alternator causing the lock up issue.

 

[Mopar1973Man]

I figured out years ago that sometimes increased load of the fan or power windows, etc , will exacerbate he AC noise coming from the alternator causing the lock up issue.

True it can as diodes get hot they might start to fail from increased loads.

Mopar1973Man's Dodge Cummins Articles - Torque Converter Lock/Unlock Issues

2006 Chrysler Pacifica watch what a bad diode does to it...
https://www.youtube.com/watch?v=MGaHaIXZioA

 

[bigfish95971]

One thing, Diodes are not the only parts to go bad in the alt causing the ac problem. Mine was a bad rotor in it. Can be rectifier too.