my battery and alt test great out of vehicle but in vehicle battery is not charging alt is testing good says no regulator reading when run charging test in vehicle but works on machine at auto parts s

Asked by Jun 05, 2015 at 12:19 AM about the 1990 GMC Sierra 1500 K1500 4WD Extended Cab LB

Question type: Maintenance & Repair

alt electrical 1990 gmc sierra 1500

4 Answers

64,415

There must be something causing this issue in the truck wiring,or could be the ECM is bad,not letting it charge the battery.

well i changed ground from battery to block but was curious about ground from chassis to firewall

64,415

Yes the body has to have good ground all so.

92,905

When you turn on the key do you see the little battery light? That light has to work, it is part of the exciter circuit, if it works then it is like T S T stated, a wiring or ECM glitch.

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