Alternator reading low voltage at idle

EDNAR

MEMBER
2005 GMC SIERRA
5.3L
V8
4WD
AUTOMATIC
180,000 MILES

Alternator replaced and now reads low voltage at 1,000 rpm's and less. The alternator was a 2 pin type. When In replaced alternator it was a 4 pin plug with the same two colored wires (brown and tan). So I replaced the two pin plug with a four pin plug. Could that be the issue? If so, how to correct it? Thanks.

2 Replies

JACOBANDNICKOLAS

MECHANIC
109,747 POSTS

Hi and thanks for using 2CarPros. Com.

It sounds like you were given the wrong alternator. Have you contacted the parts store requesting the correct one? I cannot be sure what the output of the alternator you received is, so chances are that is the problem.

Let me know.
Joe

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Sunday, November 11th, 2018 AT 5:58 PM

CJ MEDEVAC

MECHANIC
11,004 POSTS

I have been looking at your question from time to time as I answered others.

I was kind of hoping another expert might shed better light on it.

So far I have not found the 4 pin system in any diagram for your year.

Do you have any idea what the 4 pin application went on (year, vehicle. Etc)?

I guess the next best thing would be if you sent your VIN so I can get the correct diagram for your truck out of "Prodemand".

This would show exactly where the wires go.

After seeing your latest postings, I cannot figure out why you did not replace the alternator with the correct one and everything would have fit back with no modifications or "McGyvering".

Maybe it was an emergency? Maybe it can be swapped for the right one with no major money lost?

I will try to help, if I cannot, I have a lot more experts here I can rely on for assistance.

The Medic

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Monday, November 12th, 2018 AT 11:06 AM (Merged)