May 1, 2015

Air compressor common questions

By Sears PartsDirect staff
Air compressor common questions.
Air compressor common questions.

These common questions about air compressors are the ones our experts hear the most often from our customers. You might also find the help you need by checking the common symptoms and solutions for air compressors. When you’re ready to make a repair, search your model number to find replacement parts. Sears PartsDirect has the part you need, no matter where you bought your air compressor.

Why does the air compressor safety valve release air?

If the pressure switch fails to shut off the air compressor when reaching the cut-out pressure setting, the safety valve pops out and releases excessive air pressure to protect the tank. Replace the pressure switch if it's defective. Replace the safety valve if it releases air before pressure reaches the cut-out setting.

Why will the air compressor start when the tank is empty but not when the tank is full?

The check valve prevents tank air from back flowing to the pump. A failed check valve will apply high air pressure to the head of the pump preventing the motor from restarting once the tank has filled. If the motor starts with an empty tank but won't start when the tank is full, replace the check valve.

How often should I drain the air compressor air tank?

Drain the air tank daily or after each use to remove condensation. Condensate water that remains in the air tank during storage corrodes the air tank. Pull the ring on the safety valve to bleed the tank pressure down to about 20 psi. Open the drain valve on the tank bottom to release the condensate water.

Why won't the air compressor build up any tank pressure?

Shut the tank drain valve if open. Worn pump seals prevent air pressure from building up. Rebuild the pump if necessary. Check the air tubes, components and fittings for air leaks. Tighten any loose air tube fittings. Replace any leaking components.  

How do I convert my air compressor to use 240-volt power?

If the motor is convertible to 240-volt power, unplug the compressor and remove motor cover. You'll usually find the wiring diagram and instructions for converting the motor to use 240-volt power on the back of the motor cover. Refer to your owner's manual if the instructions are not on the back of the motor cover. Install a 240-volt power cord with an adequate power rating using the instructions on the motor cover or in the owner's manual. 

Can a rust hole in the air compressor tank be patched?

No, don't attempt to patch or repair a leaking tank. Modifying the tank in any manner weakens the tank structure. A repaired tank can rupture or explode. Replace a damaged tank instead of trying to repair it.

Can the air compressor pump be rebuilt?

Yes, rebuild kits and seals are available to rebuild the compressor pump. Refer to your owner's manual or part list for part numbers descriptions of the rebuild kits. Visit our air compressor repair help section for instructions to rebuild your air compressor pump.

Why does the tank pressure drop below the cut-in pressure before the air compressor restarts?

The pressure switch regulates the tank air pressure by turning the compressor on and off. The pressure switch could be defective if the compressor doesn't cycle on and off properly to maintain tank air pressure. The cut-in pressure is usually about 30 psi below the cut-out pressure. Replace the pressure switch if defective. Visit our repair help section for step-by-step instructions for replacing the pressure switch in an air compressor.

Can I operate the air compressor using an extension cord?

Yes, but make sure the extension cord is in good condition and rated to handle the air compressor electrical load. Use the shortest extension cord possible. Using the wrong extension cord damages the air compressor's motor. Follow the advice in the owner's manual to select an appropriate extension cord for the air compressor.

Can I install a muffler on my air compressor to reduce noise?

Yes, you can install a compatible muffler on your air compressor to reduce noise. Aftermarket mufflers are available for most compressors and provide varying degrees of noise reduction.

Symptoms common to all air compressors

Choose a symptom to see related air compressor repairs.

Main causes: rusted air tank, loose air tube fitting connections, bad check valve, leaky safety valve, bad tank drain valve
Main causes: bad safety valve, pressure switch failure
Main causes: loose air tube fitting connections, bad check valve, faulty safety valve, damaged or corroded air tank, bad air pump
Main causes: tank drain valve open or leaking air, leaky air tank, bad safety valve, worn pump seals, bad pump valve plate
Main causes: lack of electrical power, check valve failure, bad pressure switch

Repair guides common to all air compressors

These step-by-step repair guides will help you safely fix what’s broken on your air compressor.

How to replace an air compressor pressure switch

You can replace a broken air compressor pressure switch in about 45 minutes.

Repair difficulty
Time required
 45 minutes or less
May 1, 2015
By Lyle Weischwill
How to rebuild an air compressor pump

If the air compressor won't fill the tank with compressed air, rebuild the pump using these steps in about 45 minutes.

Repair difficulty
Time required
 45 minutes or less
How to replace an air compressor check valve

You can replace a defective air compressor check valve in about 10 minutes.

Repair difficulty
Time required
 15 minutes or less

Articles and videos common to all air compressors

Use the advice and tips in these articles and videos to get the most out of your air compressor.

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How to reduce air compressor noise

By Sears PartsDirect staff

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