Pressure will not build up past 20 PSI - Craftsman 3 gal. Air Compressor, 1.5 hp, Horizontal k

Hi, There are different posibilities. I would need more information. Was it always like that? Does the guage on the main tank and the guage on the regulator both not show more than 20psi? When the auto shut-off is triggered do you feel there is more than 20 psi in the tank?

the pressure sensor is likely defective. How old is it? take it to a Dewalt service centre

If your compressor is a piston compressor, try cleaning the check valve which comes from the pressure switch to the tank (it has a little spring and a rubber/plastic valve inside)
Otherwise check to see if it is sucking air in properly, (whilst it is running, remove the air filter, and very quickly put your hand over the air intake to see if it is sucking whilst it is at 20 psi, if not, then it may be that the valves in the head maybe either broken or not seating properly

If it is not a piston compressor, then it maybe the MPV needing some attention

Hope that helps

Hi

Perhaps it may be something to do with the setting of the pressure valve

Cheers
John

There are several causes for this to occur.
1. If it is a 20-40 switch right out of the box it may not be set correctly. I have had this happen. If it builds to 30psi and shuts right off without straining to build to 40psi adjust the Cut-Out pressure up to 40psi. There are two different adjustments on a well switch. One for Cut In / Cut Out psi and one for Cut Out psi.
2. Lack of head pressure being built by the pump can be the cause. This can be attributed to the wrong Jetting in the pump. IE: A shallow well jet/venturi on a deep well.
3. The pump may have a bad impeller, but the pump will generally really strain to build pressure and a bad impeller will be loud, like grinding at times.
4. Double check the pre-set pressure in bladder tank also.
RJ

First take off the head on the air pump and check the reed valves on the valve plate. If they got hot and warped or cracked they'll work to a point then no more pressure can be built up. Next check the pistion ring and cylinder wall. If either is damaged you'll only get so much pressure build-up then it will leak past the piston.

The problem with compressors not building pressure is usually a bad pressure switch or bad regulator. Does the motor shut off at 20psi or does it continue running and not build pressure? If the motor continues to run with no increase in pressure, the you should go over the machine looking for air leaks from your regulator back all the way to the motor. Any air leak while the compressor is running can cause the pressure to "peak" way before the intended shutoff that it is regulated to.

Check to see if air is leaking past 'pressure relief' valve. It's probably leaking and that's where all the air is going.

If you need further help, I’m available over the phone at https://www.6ya.com/expert/craig_3fa289bf857b1a3c

looks like you will have to get the diaphragm seals in the pump replaced

compressor will not build pressure