An air compressor that runs constantly is usually caused by a stuck pressure switch, air leaks in your hoses or fittings, a clogged air filter, or a demand for air that exceeds the compressor's capacity.
An air compressor that keeps running usually means it is struggling to build up pressure or cannot tell when to stop. The most common culprits include severe air leaks, a broken pressure switch, worn internal pump valves, or heavy tool usage that exceeds the compressor's capacity.
Defective Pressure Switch: The pressure switch monitors the tank's pressure and signals the compressor to stop when it reaches the cut-off point. A defective switch can fail to recognize that the cut-off pressure has been reached, keeping the compressor running.
If the cut off switch is not turning off the motor at the desired pressure, it could be due to a misadjusted switch. To troubleshoot this issue, turn off the compressor, unplug it, and remove the cover of the pressure switch. Locate the adjustment screw and adjust it to the desired pressure level.
The idle is not supposed to increase in speed when your compressor engages, rather the throttle plate should adjust at the same time the A/C engages to maintain the same RPM at idle. This will keep the idle the same with A/C on or off.
An air governor controls your vehicle's air compressor, telling it when to pump air ("load") and when to stop ("unload"). A faulty governor typically causes rapid air pressure fluctuations, constant hissing or air leaks, failure to reach or hold pressure limits, or dangerously high pressure.
To fix a high idle, start by checking for physical obstructions like a stuck gas pedal or tight throttle cable. Then, clean your Mass Air Flow (MAF) Sensor and Throttle Body, and check all hoses for vacuum leaks.
The reset button is almost always located on the electric motor itself—usually on the side or back near the terminal box. It typically sticks out as a small rubber-covered or exposed black/red button, sometimes labeled "Circuit Breaker".
Symptoms of a bad run capacitor on an air compressor motor include the motor humming without starting, frequent tripping of circuit breakers, a noticeable loss of power or reduced CFM, and the motor running unusually hot. Physically, you might notice a bulging casing, scorch marks, or leaking dielectric oil.
An air compressor typically keeps shutting off due to overheating, an electrical fault (like a tripped breaker or bad capacitor), or a malfunctioning pressure switch. The most common causes and how to fix them include:
An air compressor can run continuously for anywhere from 10 minutes to 24/7, heavily depending on its type and duty cycle rating. Portable and piston compressors are typically meant for intermittent use, while industrial rotary screw compressors are built for non-stop operation.
To shut off an air compressor properly, switch the main pressure to "OFF" instead of pulling the plug. Turn the pressure regulator knob counterclockwise to zero, bleed out the remaining air using your tools, and open the bottom drain valve to release trapped moisture.
Troubleshooting a compressor involves verifying power supply, inspecting electrical components (capacitors, contactor), and testing motor windings for shorts or opens. Common issues include a failed start/run capacitor, tripped breakers, or an overheated unit. Always disconnect power before testing components with a multimeter.
Faulty Pressure Switch: The pressure switch is responsible for monitoring the tank's air pressure and signaling the compressor to start or stop. Leaking Check Valve: Located between the compressor pump and the air tank, the check valve prevents compressed air from flowing back into the pump.
One of the first signs of a bad air compressor pump is a decrease in performance. If you notice that your air compressor is not delivering the same amount of air pressure or volume as it used to, or if it is struggling to maintain consistent pressure, it may indicate an issue with the pump.
If you allow your air conditioner to keep running, electrical power is wasted and your system sustains excessive wear and tear, which causes damage to components and malfunctions which creates the need for parts or the entire system to be replaced.
An air compressor that fails to shut off typically means it cannot reach its maximum rated pressure or the automatic switch is malfunctioning.
Air compressors typically last 5 to 20 years, depending on the design, how frequently they are used, and how well they are maintained. A portable DIY model may give you about 500 hours of run time, while industrial units can last for decades.
A manual reset pressure switch is a safety device that automatically shuts off equipment (like a well pump, AC unit, or compressor) when pressure hits unsafe levels. Unlike automatic models, it stays off until you manually push the reset button or lever to clear the fault and resume operation.
But How Do I Know If My Capacitor is Failing?
Compressor capacitor replacement typically costs between $100 and $400 in total. This price breaks down into $10 to $45 for the part itself and roughly $75 to $250 in professional labor and diagnostic fees.
Insufficient lubrication is the underlying cause of many major compressor failures, even when the initial symptom looks unrelated. Using the wrong oil viscosity, running beyond recommended oil-change intervals, or allowing oil levels to drop all weaken the protective film that separates moving parts.
Many air compressors do have fuses (or inline fuses) as a safety mechanism to prevent the motor from burning out or causing electrical fires. However, the type of protection varies based on the compressor's style and power source.
Starting up after long periods of shutdown
Slowly open the compressor air discharge valve until the air pressure equalizes between the compressor and the air net. Start the compressor. The compressor is now back online.