The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post - Alternator won't charge and reference wires are grounded

Irish1941 · 11-06-2018, 12:58 AM

Thought I replied..opps
Anyway, the "L" wire goes thru the junction block on the lower right. It's goes along valve cover then under the booster but your problem won't be under the dash. The big round hole is for ECM harness.

Like Speedy said it's just breaking connection and not grounding out. If it was grounding to the body, the fuse would pop and entire dash would stop working. All fused on same circuit.
Not sure where you are grabbing it to make the alt kick in and out, but L wire is the excite wire and is on 12v keyed. It's goes right to your gauge or lamp on the dash. That why alt starts and stops when you wiggle it. Alt needs to see 12v signal to turn on. No signal=no charge.

Check the plug first and foremost. Wiring is brittle after all these yrs and they take a beating with alternator changes & heavy handed plug pulling, corrosion, loose crimp etc.
If it checks out good, then just move along the wire til you find the bad spot.
Has to be with 10" of where you are pulling on it.

11-06-2018, 12:58 AM	#10
Irish1941 Registered User Join Date: Nov 2012 Location: Los Angeles, CA Posts: 450	Re: Alternator won't charge and reference wires are grounded Thought I replied..opps Anyway, the "L" wire goes thru the junction block on the lower right. It's goes along valve cover then under the booster but your problem won't be under the dash. The big round hole is for ECM harness. Like Speedy said it's just breaking connection and not grounding out. If it was grounding to the body, the fuse would pop and entire dash would stop working. All fused on same circuit. Not sure where you are grabbing it to make the alt kick in and out, but L wire is the excite wire and is on 12v keyed. It's goes right to your gauge or lamp on the dash. That why alt starts and stops when you wiggle it. Alt needs to see 12v signal to turn on. No signal=no charge. Check the plug first and foremost. Wiring is brittle after all these yrs and they take a beating with alternator changes & heavy handed plug pulling, corrosion, loose crimp etc. If it checks out good, then just move along the wire til you find the bad spot. Has to be with 10" of where you are pulling on it.