YC 1 wrote:
The dash light is telling you something. Why are you ignoring it? You need to put an ammeter on the output wire of the alternator. A clamp on meter is fine. I do not think you have established your alternator is capable of putting out its full capacity. A slipping belt due to the heavy load can easily cause your problem.
Thanks, I will check it out. I have been treating it as more of a curiosity since nothing bad ever happens (except for this).
BTW, that dash battery light glows dimly even when the truck is parked, so it can't be a loose belt. Been doing that for 13 years now. It does drive me crazy.