i have problem with my compressor i changed the power switch its running but the gauge pressure of the tank is not going all the way barely the needle of the gauge moving half way what will be the issue?
Before you junk it check the line from the tank to the pressure switch.
Very common for them to leak.
Next I would check for leaks where the line goes into the head of the compressor. most often all that seals it is a cheap rubber O ring.
Next check the check valve, air should be going into the tank not out of it when it shuts off.
Last would be the reeds that are built into the head on the top of the compressor, they tend to break or crack when they get old.
If you go that far may as well pull off the cylinder and check the piston, rings and the walls of the cylinder.
I've seen the piston wear off on one side which cracks the rings and scores the cylinder walls.