2nd Gen Non-Engine/Transmission Alternator charging 18V?

[BDaugherty]

So I got a call from a guy stuck a couple hours south of me. He has a '99 2wd dually stock other than the low pressure fuel system and the old school hotter ECM that you used to buy back in the early days of the 24V. He said his volt meter is pegging high around 18 volts. He swapped in a parts store alternator with no change.

Voltage regulator is in the PCM on these trucks, right? After cleaning grounds, what's the next step? Verify wiring at the alternator plug and make sure it has continuity back to the PCM? If the problem is internal to the PCM, can it be sent off from repair or is it easier to just swap in an external voltage regulator? Advice or links to a write-up would be greatly appreciated.

 

[Bob4x4]

Check batteries they can throw the system for a loop also
Those Cummins up-rate ECM s were nice

 

[DavidC]

With all the horror stories I have read here on replacement PCM's I think I would do the external regulator if that is the only symptom he is seeing. I would also check the field voltage to the alternator and wiring all the way to the PCM as you stated including the plug and pins. I really can't remember but I think there are 1 or 2 other things that need to be done for the check engine light etc. using the external regulator. The charging problem could be as simple as corroded pins. There is also a thermistor under the driver's side battery that controls charging. Has he verified with a meter that he is actually getting 18+ volts at the battery ?. May be a gauge problem ?.

Dave

Dave

 

[HHhuntitall]

Hmmmm, after a battery and wiring check, and still having a problem, I'd suggest trying to convert the alternator to self regulating. There are several write ups on how-to here on TDR.

 

[BDaugherty]

That's what I was thinking on the self exciting. I guess it's time for some searching. If anyone has a good link, please post it for me. at this point, he parked the truck, but it will be a project when I slow down a little.

 

[Bob4x4]

Why create a cl engine light and smog check fail????