Suspension wont build air when under the load

Might be the pressure protection valve stuck partially closed.
I don’t know which one it has. You can google pressure protection valve and get a idea of what you’re looking for.
@Goodysnap

 

Sounds like you're not building air pressure. That's why your fan stays on too. I'd bet you have a major leak somewhere under a load.

Big air leaks make little noise

 

You have an air leak someplace, a valve stuck, a bad air assisted fan clutch would be my most likely guess by your description.

Unplug the wires for it, this should make it not ask for air. If its leaking that will make your bags work normal until you plug it back in.

 

Gremlins in the machine,,,, okay, you got at least 3 things going on here. I don't think they are related. Could be an air leak, but you'd hear something. Ride height valves do go south, fan running while loaded sounds like a plugged radiator, and they all use a lot of fuel. If you aren't building air, could the brakes be dragging?

 

Agree. After ruling out/ repairing any air leaks I would check the leveling valve. Check that the linkage connections are not worn. Can also disconnect the linkage and operate the valve by hand. And the Pressure Protection Valve like 062 said.