So as part of my effort to get my truck (with the 300-6 engine) back into shape, I've been working on the electrical system. Replacing the voltage regulator fixed some of my problems, and replacing the alternator seems to have fixed the rest of them. However, there is still one oddity: when I first start the truck, the CHARGE light comes on and stays on. It only goes out when I rev the engine pretty good while in park or neutral, or get up to about 30mph on the road. But once it goes out, it stays out.

Just for fun, I put my meter on it. At the battery with the truck off, I get about 12.5 volts. At the battery with the truck running, and the CHARGE light on, I get 12.5 volts. At the battery with the truck running and the CHARGE light off (after revving) I get around 14 volts.

It seems as though the alternator needs a kick to 'wake up', but once it does it stays going. Does anyone have any suggestions for how to get it to wake up a little earlier, so I don't have to stare at that light?

 

After you ran it, did you re tighten the belt? Almost sounds like your belt is a little loose.

 

If the belts are tight, and it still does it, I would think that is a faulty alternator. It works when you need it though right?

The more I think about it, it could be a faulty regulator too, not letting 14v out until it is warmed up enough (by current). My thoughts are getting into theory of individual components inside the vr.

Can you get it to do it after a routing shopping stop? If so I would take it to a parts store and have them check the system when the light is on...

 

The belts (which are new) seem tight to me, but I'm going to snug them up some more next chance I get, just to be certain. If loose belts were the problem, though, I would expect the light to come back on when the engine returned to idle, or occasionally come on while driving. But once it goes out, it stays out.

It exhibits this behavior every time the truck is started, so it would be easy to have the parts store test it. However, could I test the alternator output myself? If I got under the truck and put the meter directly on the alternator, what output should I expect to see? This is a 65A alternator, which replaced the original 40A the truck came with.