Engine/Transmission (1998.5 - 2002) AC voltage in Electrical system?

[SAronson]

I've been having problems with transmission/ APPS, etc. , and have been trying to diagnose. After reading many posts both here and on the Net, I checked for AC voltage in the electrical system. I found 30vac at the alternator and batteries. Is this a leaky diode? And, do I just need to replace alternator, or can I just replace diodes?

 

[B.G. Smith]

You should be able to change the diodes. bg

 

[SAronson]

Source for diodes? Napa does'nt list the diodes. CEL came on again... #1693 is the only code.

 

[SAronson]

Cleared the code,and through in a new rblt alternator from Napa. I just got back from a test drive, and the transmission is shifting normally and no surging from engine. In fact, it seemed to run smoother, and had better response. I'm assuming the alternator (which is known for causing electrical problems with our computer controlled trucks) had a degrading diode(s) for some time and all my "fixes" (Apps, voltage filter, etc. ) were just band aids. The problems that I was experiencing (surging, not shifting to first at a stop, erratic TC lock ups, and rougher running) were all voltage issues. The alternator is what produces the electrical power for our rigs, and if it's not operating correctly, then the "sh%t" flows down stream and creates all sorts of issues with our sensors, ECM, PCM, APPS, etc... . Time will tell, but I'm impressed with how well the trucks runs now. BTW, I was not having a charging issue... . I hope this feedback helps someone else with their rig.

 

[JLandry]

That's great news!



Please be sure and post an update after awhile so we know the fix held up.



I'm keeping my fingers crossed for you.



John L.

 

[SAronson]

Just wanted to give an update..... all is still good! Truck has been shifting down into first at stops, no CEL's/codes, and overall operation seems normal. I have a 600 mile trip for Thanksgiving comming up, and this should be a better test than driving around town.