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The alternator is not charging battery?

Tiny
ED101
  • MEMBER
  • 2007 PONTIAC G6
  • 3.5L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 100,000 MILES
Replaced battery and alternator twice now on third alternator. Battery is reading 12.5 volts on initial startup then drops to 12. The alternator is putting out 1.7 volts at terminal we have verified all wires for power from battery to alternator are good, fuse is serviceable. Not sure what to do next. Please help
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Saturday, August 19th, 2023 AT 1:22 PM

1 Reply

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,217 POSTS
Hi,

I attached the wiring schematic for the charging system so that you have a reference. See pics 1 and 2. I had to cut it in half to make it readable. I did overlap the two so you can follow from one to the next.

If you are certain the fusible link is good and the red/black wire at the alternator has 12v at all times, we need to consider a wiring issue at the ECM or even the ECM itself.

The remaining pics below are diagnostics for testing the alternator circuit. Take a look through it and let me know if you are comfortable performing them.

Take care,

joe

See pics below.
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Saturday, August 19th, 2023 AT 10:12 PM

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