I have a 95 (?) k3500 dually dump truck

When accelerating, the voltage drops. Under a heavy load (bed full of material), the voltage drops to the point the engine cuts out. I've changed the alternator and battery and checked all the wire connections.

I'm stumped what the problem could be...

 

What size alternator? Is it new, used? I'd suggest have it checked even if new.

 

Brand new. Even the one I changed out was only 2 years old...

 

Disconnect the dump load, see if that changes the voltage.

 

What you post is, you're feeding a short

 

std or automatic trans?
how are the drive belt and tensioners. if std, are the thrust bearings worn out causing the crank to move forward under extreme load? load it up and watch for crank and engine mount movement.

so it only does it when in drive?
did you do voltage drop tests of the insulated and grd circuits for the charging system when the system is under load?

 

Finally figured out the problem..

A bird and mouse (!!) made a nest in the air filter. Go figure...

Under load, the engine was cutting out... I have no idea why it manifested itself as flickering lights, radio reseting and voltage drop. Now its cleaned and filter changed the trucks runs like a champ.

thanks for the help and tips.