AMC Concord electrical problem

I have a 1978 AMC Concord wagon, automatic, 304 eng. with 64,000 miles. This year my headlights started flickering after being on about 4 or 5 minutes. I have a new battery, replaced the dimmer switch and fuse, checked out the voltage regulator and alternator and they are all ok. I suspect the problem is in a “relay switch” or the headlight switch but if I turn the lights on for 15 minutes they do not flicker, flash or have any “hot flash symptoms” of any sort. So these components work fine if the engine is not running. What do you think my problem might be?


Loose connection? With the engine off, turn the lights on. Pull and shake every wire, while watching the headlight, you can find. Don’t forget ground straps, and ground cables.

How did you go about checking the voltage regulator? If you put a volt meter across the battery terminals, do you have rock-steady voltage at idle?

EDIT: Didn’t see what hellokit had already posted. I agree with him, a wiggle test is in order.

You are probably using a digital multimeter. You may need to use an analog meter to see the voltage variation. You are looking for a battery voltage varying from 14.5 down to 13. That would be enough to be seen in the head lights. The variation will be synched with the head light variation. If you do see the variation at the battery, put the meter on the field wire from the regulator to the alternator (I think this still had the separate regulator.) If you see a wild variation here you have a problem with the regulator, the alternator field windings, or the slip ring brushes. The first thing I would do is to check the length of the alternator brushes and the condition of the slip rings.

Let us know what you finally discover