Key Takeaways:
- Air compressor humming is typically caused by electrical issues such as insufficient power from extension cords with inadequate gauge ratings, which create power draws that prevent the motor from starting properly.
- Common causes include malfunctioning unloader valves that trap excess pressure and prevent motor startup, clogged intake filters that restrict airflow and cause the compressor to stall, and blocked tank check valves that increase internal pressure.
- Faulty capacitors that store electrical energy for startup will eventually fail and can be damaged prematurely by voltage spikes, corrosion, or high temperatures; if the hum persists after checking filters and relieving pressure, a professional repair or replacement may be necessary.
Compressors of all sizes produce noise and often get quite loud. If the sound is an unusual one, however, it could be practically deafening. Air compressor humming is common at startup but could also happen during use. If that happens, you can also experience a sudden drop in tank pressure. We’ll let you know what air compressor humming means, why it’s happening and what you can do about it.
Common Reasons Why Your Air Compressor Is Humming
Air compressor humming is a sign of trouble. With equipment, humming usually signals an issue with electricity. With a little troubleshooting, you can get to the bottom of the hum from an air compressor. In many cases, you can even resolve your issue on the spot.
Not Enough Power
Compressors are highly mobile, and you can take them anywhere you need to as long as you have access to power. If you need to work away from your power supply, make sure you have an extension cord rated to handle the job. Extension cords come in gauges. The lower yours is, the better suited the cord is for heavy-duty and outdoor applications. Wires with higher gauges (typically 14 and above) can cause power draws that make your air compressor hum.
A Malfunctioning Unloader Valve
Unloader valves release excess pressure from the tank. If your unloader valve traps air inside your compressor, the stress will interfere with the motor. If the motor is unable to start because of excessive air buildup, the air compressor will hum. To troubleshoot yours, power your compressor down. Using the hose, empty the tank to relieve pressure. Turn the compressor on. If it works, your unloader valve is to blame.
Clogged Intake Filters
Air compressor intake filters prevent dirt and crud from getting into your machine. Over time, the trapped media builds up, restricting airflow into the motor. Without enough air, compressors will stall, and yours may hum when you try to restart it. To check and see if your air filter is the cause of your air compressor humming, unscrew and remove it, then restart your machine. If it works, you need to clean your filter.
A Blocked Tank Check Valve
Blocked valves stop the air inside your tank or compressor header from coming back through the inlet line after shutdown. If the valve gets stuck open, it can cause damage. If it gets held closed, it can cause a pressure increase that often leads to air compressor humming.
Tank check valves typically attach to the tank where the pump-head line connects. Remove yours and clean any debris from the valve. If it remains stuck, you need a replacement.
Faulty Capacitors
Compressors require a lot of power. Inside these machines are capacitors that provide the additional energy needed to kick your compressor into gear. These devices act like batteries and store electricity.
Like batteries, they will eventually reach the end of their useful life. They can also have their function reduced much more quickly if they take damage from a voltage spike, corrosion or high temperatures. In this case, your best bet is to call a professional repair company or replace your compressor.
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