Pressure switch won't restart compressor when pressure drops

CheckMany switches have a lever that must be fully in the Auto/On position. Some trip to Off if the motor overloads.

FixSet lever to Auto; if it trips repeatedly, investigate overload.

CheckLook for a red reset button on the motor. Motor case very hot. Check whether the unit has been running at excessive duty cycle or with a hard-start (check valve leaking back, unloader not bleeding).

FixLet cool, reset, then fix the root cause: improve ventilation, repair unloader, check voltage under load.

CheckWith pressure below cut-in and power ON (qualified person, PPE), measure voltage line-to-load across each pole. Line voltage present on line side but not load side = contacts not closing.

FixReplace the switch. Don't file contacts — it's a temporary fix at best.

CheckNote gauge pressure when the motor finally starts. If it starts at, e.g., 60 psi when you expect 95, the differential screw has been opened up.

FixAdjust the differential nut (small spring) to restore your band — typically 20–40 psi on recip units. Verify with a test gauge.

CheckLOTO, remove cover, inspect terminals for burnt insulation, loose screws, or aluminum wire on copper-rated lugs.

FixRe-terminate with proper wire size and torque.