If the safety valve trips at operating pressure or well below the relief set point, replace the safety valve because it's broken. If the tank is over pressurized, the pressure switch isn't shutting off the motor when the air tank fills to the cut-out pressure. Move the pressure switch lever to the off position. If the compressor continues to run, replace the pressure switch because the switch isn't shutting off the compressor motor. If the compressor shuts off when you move the pressure switch lever to the off position, pull the safety valve ring and release all air from the tank. Switch the pressure switch lever to the on position and allow the tank to fill. If the compressor doesn't shut off when the air tank fills to the cut-out pressure, replace the pressure switch because the switch isn't shutting off the compressor motor when tank pressure reaches the cut-out pressure.
These repairs may help solve your air compressor problem
Replace the air compressor safety valve
The safety valve pops open to relieve excessive air pressure if the pressure switch fails to shut off the air compressor at the cut-out pressure setting. Replace the safety valve if it leaks or pops open at normal operating pressure.
Replace the air compressor pressure switch
The pressure switch turns the air compressor pump on and off to regulate tank air pressure. If the compressor isn't cycling on and off to fill the tank, replace the pressure switch.
If your air compressor won’t shut off after reaching full cut-out pressure or won’t start again after tank pressure drops, the pressure switch might be the problem. The step-by-step repair guide and video explain how to replace an air compressor pressure switch in less than 45 minutes.