Alt good but no charge

[diesel-lam3722]

I had my ALT tested and tested just fine. I just bought it so that didn't surprise me. I was driving down the hwy trying to get up to speed so my overdrive would kick on and it didn't want to shift and I had it floored in 3 gear and suddenly my dash voltmeter started bouncing significantly and eventually stopped and stuck on about 11 volts now. I chcecked the gap on the CPS and that checked out and my battery is brand new. thanks for any input I need to get my truck going. its a 1993 dodge w250 diesel. 4x4

[762frmafr]

Have you checked you battery cables? Or the cables running from the alternator?

[ellis93]

while the gap is very important on the crank sensor,it does not mean it's not defective. They do go bad. Without it working there will be no a/c,no o/d,and no alt charging. The computer does not know the engine is running and won't activate those items.

[JimmieD]

Good clean grounds are every bit as important as power connections. Need good clean bare metal to bare metal connection at engine ground strap to block and to body connection. Also clean bare metal to clean bare metal from body of external voltage regulator to where it mounts to truck body. Clean bare metal connection from battery negative cable to where it grounds to body/chassis.

Sometimes there's hidden corrosion on battery cables. Cut back insulation on cables next to lugs and look for green corrosion hidden there. If there's corrosion it can't be cleaned off, cable must be replaced. Afterwards if no corrosion the cut part can be taped and re-insulated with Scotch 33+ electrical tape - best electrical tape out there for vehicles.