Who likes an air compressor that never turns itself off? You do a job, you walk away and then you hear it running. It draw power.
It wastes energy. It create heat. It also annoys the crap out of you.
So what’s wrong with it? Most people think their unit must be defective. Guess what?
More often than not they’re wrong. Almost all issue have to do with a simple settings error or a minor mechanical problem…not something catastrophic. Instead of making a trip to the hardware store, troubleshoot it.
Not only do you save money by not purchasing a new compressor, but you also don’t have to spend five bucks repairing a problem that costs you $5 to repair. The key to understanding how and why the machine will continue to run is to look at the entire pressure system. A compressor doesn’t “think.” Instead, it reacts to the pressure of air.
Common Reasons Compressor Runs Continuously
Understanding the Pressure Switch
Without a true signal to shut off or with an improper signal, the motor continue to run. This is a pressure switch. The pressure switch is always the first suspect, and for good reason.
The pressure switch are the brains of the system. What it do is monitor the pressure in the tank and when it reaches the cut off point, it turns off the power to the motor. The internal contact can corrode over time and burn out.
The result is that it doesn’t open the circuit anymore. When you see the tank full and the motor continue to run, you know something’s wrong with the switch. A new one are easy to replace.
You’ll need some basic electrical knowledge and a multimeter to verify the problem.
Checking Clogged Intake Filters
More quietely, the culprits is clogged intakes filters. On the side of the motor housing is the air filter.
Its purpose is to block the pump from sucking up dust. If this filter become filled with junk, it restrict air flow into the pump. Less air can enters, causing a vacuum in the system.
This affect compression. The pump chokes and can’t build enough pressure to reach desired levels in the tank. The pressure switch continues waiting for a signal it will never get.
The motor just runs…endlessly…in vain. Changing or cleaning the filter are an easy solution. It instantly opens up the airflow.
Locating Air Leaks
The number one cause is air leaks. Examine all your hoses, fittings, and even the drain valve on the bottom of the tank. As soon as the compressor fills the tank, a tiny leak will cause the pressure to drop quickly.
Then the system goes into bleed/ fill mode where it fills then bleeds out air. This can be recognized by a very distinctive hiss that’s usually coming from the leaking spot. After the compressor turns off, listen closely.
If you hear the pressure dropping then you found the leak. O-ring replacement or tightening of fittings resolve this.
Adjusting Pressure Settings
It could also be that the pressure setting is too low: On most craftsman compressors there is an adjustment on the pressure switch.
That’s the spring one. You will notice it will cause the compressor to turn on and off quickly if set too low. When the interval is brief, it simply sound like it’s running all the time.
This put extra stress on the motor. Go to the manufacturer recommended PSI for your model. Then adjust the screw clockwise to raise the cut off pressure.
This gives your tank time to fill correcty.
Inspecting the Check Valve
Last but not least, inspect the check valve. This one-way valve is located in-line between the tank and pump, allowing air into the tank but not letting it flow back.
When your motor shuts off, the check valve should of prevent air from escaping back into the pump head. Otherwise you’ll get a hissing or banging noise every time the motor turns off. But more importantly, it will block proper pressure build up.
To overcome the backflow, the pump must work harder. If you’re hearing air escaping towards the pump, replace the check valve. A running compressor is typically an easy fix.
Check all your air filters first, then look for air leaks. If that doesn’t help, then go for the pressure switch. Spend a few minutes checking things out and save yourself hundreds of dollars.
It is quiet in your garage.