Compressor pressure will reach approximately 100 lbs. and then the pressure relief valve kicks on and will not go higher or shut off.

SOURCE: The compressor relief valve keeps popping, compressor runs

What pressure is it popping off at? You might have to adjust the pressure switch to a lower setting.

SOURCE: once compressor reaches 125 lbs. pressure, the

Generally, the safety/relief is set to 140 to 160psi. The pressure setting is stamped on the side of the valve. Replace the valve if it will not hold stamped pressure(cost about $6 at Lowes Lumber).The pressure switch is usually set at the factory to 120 - 130 psi. The unloader part of the pressure switch will not release backpressure unless it reaches set cut-off. The 1/4 inch line attached to the pressure switch connects to air discharge tube at the intank checkvalve (brass valve). The safety valve should very rarely release pressure, only when pressure switch malfunctions and allows pressure to reach up to 160psi. The tank will hold over 300psi so dont worry about the 160psi safety. I am not sure about your exact model number or brand, however most small compressors work the same and share similar parts. For manuals to other similar compessors to to www.dewalt.com. Here you will find manuals to dewalt and porter cable compressors. I prefer to use generic replacement parts from www.grainger.com or from Lowes Lumber. These parts will cost less than factory replacement. If you need to replace the pressure switch, use SquareD brand from grainger. Watch fitting sizes and pressure range. Good Luck on your repair.

Anthony Hill

• 50 Answers
• Posted on May 11, 2009

SOURCE: Over Pressure

I suggest trying to adjust the pressure switch, however, it is more likely that the pressure switch is bad and will need replaced. These can be purchased at most hardware stores or www.mcmaster.com. After you install it, you will need to readjust it to the pressure it was originally set to so as to not overpressurize the tank. Overpressure is very dangerous so do not use the compressor until it is repaired.
Best wishes!

SOURCE: I have a Porter Cable

I believe you have a head valve or piston ring problem. The parts you replace are suppose to leak. It is a safety feature that doesn't allow the motor to burn up before the pump warms up. Kind of like a soft start feature. If you look on the breakdown part number 107 Kit Valve Plate is what you need to inspect. Sounds like your valve plate is either worn or damaged. If you go into the pump you will have to get part 103 also which is a gasket kit. Or you can try to salvage the old gaskets.
If the valve plate is ok you will need to inspect the rings that go around the pistons. Some times you will get one that gets brittle and breaks off scarring the cylinder. Look for these two things, I am pretty sure one of them is the problem with your compressor.

SOURCE: Relief value releases and will not reset

Likely the check valve is bad or has contamination on the seat. The result is the pressure will bleed back out the compression relief valve which is often as part of the pressure switch.

If the safety valve is the one that is bleeding, then the pressure is set too high at the pressure switch.