I need help:shaking:
a. My 1990 RRC 3.9 Alternator is producing both AC/DC voltage. How can this be and do I need a new one.
b. Could it be the cause of a rough running motor?
c. Where and what type does everyone recommend? Thanks

The output should be a rectified AC wave. Basically a series of pulses from 0-14.4ish volts.

If you've got voltage swings right into negative, then your rectifier is shot.

And, yes it can cause rough running. Does it run worse the more accessories you turn on? If so, than it is definitely the culprit. I seem to remember mine was the worst around 2500 rpm.

Try Will Tillery for alternators...1-434-251-9331

Your alternator is a three-phase device. There are three diodes whose job is to rectify this to DC. There should be no detectable ripple using standard shop measuring tools.

you have lost a rectifier diode and it is now conducting on both side of the wave, hence the AC.

You do not need an entire new alternator, although it may be more realistic to replace the device. Note, you also probably have a significant voltage/current draw through the one diode that if it isn't already, will likely result in the battery dying.

Yes, this can cause rough running.

PT

And it will quickly and randomly kill every electrical device on the vehicle....

Go find an auto electrical shop and have it rebuilt or buy another.

Does anyone have a source for just the voltage regulator on these alternators?

Does anyone have a source for just the voltage regulator on these alternators?

discoweb.org. A gentleman over there just posted a list of suppliers. Be aware that disassembly of the magnetti marelli alternators is not for the faint of heart.

Ahhhh - Marelli...

One of the few vendors as bad as, if not worse then, Lucas

Imagine my surprise when I was in Oregon to see a guy wearing a Magnetti Marelli bicycle jersey. I wondered if he had any idea how poor their products were. I can just see Pendy wearing a Lucas bicycle jersey (I do not wish to see him in the bike shorts though :flipoff2:).

Because of these types of coments, I was unsure of rebuilding the stock unit on my '94 DI. I put in a Premier Power alternator and the output was about 160 amps.

It worked great.
You can even get the welding box with it for the trailside repairs.:D

does the premier power alternator use a marelli case, or is it a delco/delphi case adapted to fit? any pictures of it?

Imagine my surprise when I was in Oregon to see a guy wearing a Magnetti Marelli bicycle jersey. I wondered if he had any idea how poor their products were. I can just see Pendy wearing a Lucas bicycle jersey (I do not wish to see him in the bike shorts though :flipoff2:).

Doesn't marelli make all the efi controllers for f1 cars?

I think they do harley stuff too

The one I had was a Delco case. It looks like they modify the original alt/case now. They have also gone up about $300 too.


http://www.premierpowerwelder.com/specs/PP185.html


I can't remember the other choices right now.

Our very own Pendy sells GM alternators and the hardware to make them work. They are available IIRC in 120 and 150 amp versions.

Knowing the good guy he is though, he's probably out helping search for that poor girl in Overland Park and won't be available until they find her.

PT