Won't build pressure
Compressor struggles and slips the belt when it reaches 40/50 lbs.........new belt, old belt, same result.....pressure regulator maybe?
I don't think that the pressure regulator has anything to do with this compressor problem, Darryl.
If I understand your note correctly, when the pressure in the tank gets to 40/50 PSI, the belt jumps off?
That suggests to me that the pump sheave is slowing, and since the motor sheave is running at the same speed, a slowing pump sheave might cause the belt to jump.
If my guess is right, why is the pump slowing?
See the troubleshooting section on the sitemap page for info about why an air compressor runs and doesn't build pressure.
I'm thinking check valve, pressure valve, intake valve, binding piston... could be a number of things doing this.