Looking for ideas on what might be wrong with my truck. It is a 5.4l F250. At 3300rpm the battery light comes on and voltage (gage) starts dropping. Lights go dim if I leave it there long enough. Let off the gas to below 3k rpm and idiot light goes off and everything returns to normal. Was thinking belt, but not sure if serpantine would have this problem. What do you guys think? Alternator?

Dave

You could take it to Chevy dealer and trade it in. That would fix it

Actually Dave I had a similar problem with my '98 Chevy. I took the alternator off my '97 plow truck and stuck it on the '98. That cured the problem. Then I went and got a new alt. for it. I did that after checking battery and ground connections. It seemed that at higher RPMs the old alternator was having trouble providing juice to the ignition and electrical system. Not sure why, maybe more of a drain due to needing more/quicker spark??

Anyway, it your alternator is the problem try to find a used or rebuilt one. New ones are expensive. Good luck.....dude.

Bill

Sounds like the regulator in the alternator, pull it off, take it to a shop and have it testsd.

Thanks fellas. Never seen this one before, but thought probably the alt.

Dave

Sure enough, turns out it was the alternator. Just installed and new one ($125 btw) and everything is a-ok again. Hard to believe I got good advice from a chevy guy

Thanks fellas,

Dave