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Charging problems

Tiny
JMONTHEI
  • MEMBER
  • 2001 CHEVROLET 3500
  • 8.1L
  • V8
  • 4WD
  • AUTOMATIC
  • 120,000 MILES
New alternator, new battery, The 2 small wires that come from the PCM have 0 voltage. Is the PCM bad or is there something else in the equation that I can do?
Friday, December 6th, 2019 AT 3:46 PM

3 Replies

Tiny
94 TRANSAM
  • MECHANIC
  • 680 POSTS
Hello,
Make sure the fuse in the diagram below is good.
Trace the pink wire and make sure you have voltage at both ends and no reading to ground.
Make sure you have 12v at both ends of the black/white.
Make sure the gray to dark green splice under the dash is good.
Confirm voltage on dark green side of splice.
Confirm 0 volts on red at alt not just at battery to make sure its not a junction block issue.

Let us know what you find out.

Rich
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Friday, December 6th, 2019 AT 6:34 PM
Tiny
JMONTHEI
  • MEMBER
  • 2 POSTS
All that checked out. The two small wires coming out of the alternator have no voltage to them. And on the 4 pins on the alternator it’s the middle two that the wires go to. Where do those wires go?
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Monday, December 9th, 2019 AT 7:59 AM
Tiny
94 TRANSAM
  • MECHANIC
  • 680 POSTS
The brown and gray go to the PCM. I would pierce the wires about an inch from the plug and see if you have voltage there and the wires are broken at the plug. If not check them at the PCM. Also test the alternator case to the negative battery terminal and make sure the alternator is grounded.

If you have no voltage at the PCM then it is bad.

https://www.2carpros.com/articles/how-to-use-a-voltmeter

Rich
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Monday, December 9th, 2019 AT 4:49 PM

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