Hey all,

I know the light flickering issue has been talked about, but mine seems a bit different. So I have a new voltage regulator and my alt is good. Batt is good as well. So when I replaced my voltage regulator originally the flickering stopped. The flickering recently started again,but after about 5-10 minutes of the engine running. I thought maybe it was a fluke, but its continuing to do it. Truck is a 74 250 with a 360.

Thanks in advance for any info!

 

Have you measured the voltage while it's flickering? By definition it's a regulation problem, the question is what's causing it.

My WAG is neglected grounds, or specifically the ground reference of the regulator itself must be at the same potential as the alternator and battery, all three. If it's "floating" with respect to these it's going to want to go high side. Where is it mounted? Try another heavy jumper wire from regulator case to alternator itself, clean unpainted spot. See if the problem goes away. A related problem is old engine, frame, and firewall ground and starter battery cables etc. These will kill alternator efficiency. If they are even close to original replace them on general principles. Trust Me.

 

Thanks for the reply Ted. The regulator is mounted between the batt and radiator mount. I'll have to double check the painted surface issue. I have new grounds from the batt to the frame, frame to engine. I'll check the rest and get back to ya.

Thanks again!

 

Has the engine ever been pulled? Sometimes ground straps are forgotten or not connected after reinstallation, loose etc. Let us know what you find.

 

The stock alternators in these vehicles are lucky to put out 40amps (or even 30) max, and at idle, they are barely enough to keep a GOOD battery charged.

The flicker might be a bad diode (or more than one) in the alternator. The alternator will "test good" on the bench, because it'll put out enough voltage to be within spec, but one bad diode will cause the voltage coming out of it to have a "ripple" and can drive the regulator nuts.

Is it the old big "thick" regulator, or a newer thin style? The thick regulator actually has mechanical relays in it, and the contacts can get worn from arcing.

 

The alt appears to be old so that might be the culprit. I had orieillys test it a year ago and it checked out fine when I originally noticed the flickering. The regulator is new from Summit.