I have a Simair compressor (2 cylinder) that recently started giving me headaches. The motor will pump the tank up to the required pressure (65-70psi), but when the pressure drops from use, the pressure switch engages (about 45-50psi) but the motor will only hum (doesn’t actually engage) until there is no pressure left in the tank, at which point it pumps up again. I’ve cleaned everything from the heads to the tank with no change. I’m pretty sure the pressure switch is ok. I have a feeling it may be a motor problem…Any help would be appreciated before I use it as a boat anchor… MC
On compressors there is a non-return valve in the airline coming from the compressor to the tank. It sounds like yours is bad and is allowing pressure to be put on the pump which could hurt the motor. You might want to contact the manufacturer to see if you can get that part.
Mike
I Agree with Mike. The hum sound is the compressor motor trying to start but it is unable to because the pressure in the compressor cylinder is the same as in the tank. This could be caused by a bad check valve or because the motor is just getting old and tired.
Be aware that when the motor does make that sound it is drawing an excessive amount of current and will overheat very quickly. This can lead to damaged armature windings and insulation and commutator contacts. You should turn it off immediately when it does that.