What Jim said. Either the unlaoder or the start cap. Try the unloader
first.

Jim Levie wrote:

On Sat, 27 Nov 2004 01:06:22 +0000, habbi wrote:


I have a problem with my 4 hp cambell hausfeld oiless direct drive air
compressor. When empty it will start and work fine but if there is 50 +
psi in the tank the motor tries to start and the thermal overload keeps
tripping out. I checked the check valve and it is clean and moves freely,
also the unloader valve is clean and seems to work fine. Could the problem
be in the motor, or its capacitors? Any other ideas? Thanks


That sounds like the compressor isn't unloaded. Either because the
unloader isn't functioning or because tank pressure is leaking back into
the compressor. You should be able to find out what's happening by
cracking the output connection right after the unit cycles off at
pressure. Evidence of high pressure release would indicate that the
unloader isn't working. Cracking the output connection after the unit has
sits a while with the airtank above 50psi will tell you if there's leak
back.

It is also possible that there's a motor problem. Swapping out the start
capacitor would be a pretty cheap diagnostic.