walexa

In 2009 I replaced my alternator with a high performance one from PA Performance. The one from PA Performance has a signal wire running from the ignition on wire.

The problem I have been experiencing as of late (for over two months off and on) is the voltage on my gauge will drop like the alternator is not charging at all - maybe for a minute but sometimes for 10 minutes or more. Sometimes it works steady for days. I know the voltage is actually dropping because the lights dim in sync with what the gauge is telling me. I know the 'trigger' wire is good and supplying constant signal.

Is this the computer causing the problem? Is it the alternator? How can I test either? The hard part is that it is so sporadic. I don't want to just throw parts at it either.

Thanks in advance,

Waylan

infidel

It's somewhat common for the voltage regulator portion of the PCM (computer) to fail but the other functions be fine.
Some people overcome this with an external voltage regulator.
You could install one just for testing purposes and see if the PCM is in fact the problem. Voltage regulators are relatively inexpensive.
Instructions> https://www.dieseltruckresource.com/...n&onlynewfaq=1

walexa

Thanks for the reply Bill.

I got in touch with PA Performance again yesterday and talked to someone more knowledgeable. The first time I called the guy I spoke to didn't know much. The guy yesterday was pretty sharp. The alternator I have is self regulating, so it can't be the regulator in the PCM. He said he's never seen one of theirs do this. Yesterday I checked the 'trigger' wire and didn't find any continuity issues. By 'trigger' wire, I mean an 'ignition on' wire that excites the alternator.

Anyway, when I replaced the alternator, the OEM one had about 200k on it and there was a chirping noise that I thought was a bearing going out. New alternator did not fix chirp. Anyway, I still have the OEM one. I will completely replace the 'trigger' wire, and if it keeps acting up, the guy at PA Performance said he would send me a next day shipping label for him to look at the one from them. So I can swap in the OEM one for a few days.

Anyway, looks like it is definitely something with the alternator or my wire going to it.

Waylan

infidel

Since you have a self regulating alternator I would assume that it's not connected to the PCM then?
If it is it seems to me the alternator could be getting mixed signals causing problems.

walexa

You are correct - I realize that was not clear from my original post - at the time I wrote that I was not clear on it either.

My second call to PA Performance and the tech clarified to me that his alternator with that 'trigger' wire is self regulating. I guess it's possible that I have a intermittent connection for the exciter wire - I'll have to wait and see.

I never did have issues with the OEM alternator - so the regulating portion of the PCM may still be good.

Waylan

infidel

Common regulator problem is a bad ground.
Some folks will run a wire from the negative post on the passenger battery and connect it right to the alternator.

walexa

Hey thanks Bill!

I am going to try that today. I assume that I can just loosen one of the mounting bolts for the alternator enough to get some of the copper wire in between to ground directly to the alternator? I don't see a place on this alternator for a ground. Or maybe one of the smaller bolts that hold the alternator together?

Last couple times the voltage has dropped, when I brake to get out and check voltage on my trigger wire it starts working before I can stop - makes it very hard to diagnose. Checking the ground sounds like as good of an idea as any.

Anyway, thanks again. I'll be posting my results.

Waylan

walexa

Ran a dedicated ground wire from negative battery post and attached other end under assembly nut on alternator. Alternator still acted up today.

Obviously the issue is with the alternator............

Will post update when I get around to it. Double-edged sword here - it just acts up once in a while, which does not absolutely REQUIRE replacement now, as it is charging 95% of the time. This encourages me to troubleshoot. If it would just go out I would be forced to replace it.

Anyway, I will get around to working on it real soon, maybe tomorrow or Sunday.

Waylan