# Battery light stays on



## JayCoburn (Oct 3, 2015)

Hello,
seeking some help on '66 lemans (326). My battery light remains on while car is running. To be specific it is very dimly lit. Is this a ground issue ?
I had the alternator checked; it's good & replaced voltage reg with a better quality one. Any suggestions on where to start ?
Thanks


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## BearGFR (Aug 25, 2008)

:lol: Man oh man, I chased the same problem and the solution is not at all obvious. Check all your fuses and look for a blown one. Here's what happens: The way that light circuit works, is as soon as you turn on the ignition power flows to "one side" of that light (through one of the fused circuits) and turns it on. When the engine starts and the charging system is working, a different path sends power to "the other side" of the light. Since both sides are seeing the same power, no current flows and the light turns off. If the charging system fails, then again there's only power to "one side" of the light and it comes on. Problem is, the same thing works in reverse. If the only power source to the light is that coming from the charging system, it's going to be on. When you turn the ignition on but don't start the engine, does the light come on? It should. If it doesn't, then there you go - the problem is on the 'ignition switch' side of the light circuit. Even harder to find can be a "dim" light problem. That happens because with the engine running, the light is seeing different voltages - higher on one side than on the other - so that just a tiny bit of current flows through it. Look for a bad/weak connection 'somewhere'. :banghead:

Good luck!

Bear


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## 05GTO (Oct 6, 2004)

Here is a wiring diagram for the 66 charging circuit, if the plug on the voltage regulator is reversed that may cause the battery light to illuminate. Verify the top wire of the plug is brown.


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## PontiacJim (Dec 29, 2012)

Had that happen on a '70 Judge I used to own as a kid. Replaced the battery, Alt, & voltage regulator with no success. My battery would eventually run down with all the new parts. Finally found it. It was a broken wire inside what appeared to be a good looking wire. It was the wire that come off the alternator and ran along the intake manifold. The original engine had been removed and a later model engine installed. I figured someone had pinched the wire during installation. 

Might be why I got the car for $350 around 1981 and drove it home because the previous owner got fed up with the dead batteries and could not find the cause. Took me a couple months to sort it out, testing wire by wire on all the wiring for the charging system including up under the dash. Once fixed, never had a problem again with dead batteries or the light glowing dimmly on the dash.


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