There’s a particular type of nervousness that comes with an air compressor that won’t turn itself off. It sits there filling the tank, waiting for you to pull out your nailer, but motor hasn’t cut off yet. This isn’t right; it should of tripped the pressure switch by now.
But no, it just hums along building pressure, pressure that’s becoming dangerously high. Your trusty tool seem to have gone insane. It is frustrating and there is very obvious evidence something’s wrong with it.
Typically, this isn’t an ominous piece of machinery malfunction. It’s typicaly a tiny piece of equipment that does major task poorly. The compressor’s brain is its pressure switch which signal the motor when to turn on and off.
If the brain get confused, everything fail. Knowing why prevents unnecessary replacement purchases. Knowing why keeps you from forcing a tool to work while potentially putting yourself in harm’s way.
Common Causes And Fixes For DeWalt Compressors
The Pressure Switch
A stuck pressure switch are also pretty typical. A pressure switch sense pressure inside your tank by way of a diaphragm and then trip a mechanical lever which cut power to your motor. Whether it’s dust, oil or moisture, it will gum up that diaphragm over time and cause the lever to stick in the “down” position.
Stuck Pressure Switch Diaphragm
In other words, the switch think your tank is empty and your tank is not empty. Your motor continue to run, thinking there is still work to be done. You can typicaly clean out the switch contacts and make sure the diaphragm slide freely.
It’s a dirty job, but it’s usually fixable. On occasion the issue isn’t the switch at all. It’s valve that runs from the tank to the motor.
Faulty Unloader Valve
When you shut the motor down, unloader valve relieve pressure on the pump head. If your valve has stuck closed, it will trap the pressure in the line. The pressure switch think there is too much pressure in the line and is unable to equalize with the tank.
What happen? Your motor won’t shut down correctly. A sticky valve can be freed by spraying some valve cleaner into the unloader port.
That’s a five minute fix versus a hundred dollar headache. The thermal overload switch have blown. These are typicaly found in motors that do not turn off but act erratically as well.
Blown Thermal Overload Switch
They should shuts down completely when they trip. But sometimes an intermittent overload allow the motor to continue running until the pressure become dangerously high. This is supposed to be a safety device to prevent the motor from overheating.
If the motor are running too hot, there is something wrong with ventilation or airflow, and the compressor is telling you so. Look at cooling fins and clean out any debris and sawdust. Airflow matter more than most people think.
Leaking Relief Valve
A quick check should also be made of the relief valve. A relief valve is a safety valve and if you have too much pressure above a safe level (typically 150 PSI), it release the excess air. Without a good relief valve, your tank won’t ever hit the cut-off pressure.
The pump will run constantly because it’s attempting to fill up a bucket that has a hole in it. You’ll notice a hiss sound coming from near the tank. Replace the seal on the valve or tighten the valve and stop the leak.
The proper pressure cycle will starts again. Lastly, check out the plug and power cord. The electronics in the switch act up if there is a voltage drop from a loose connection.
Power Cord and Voltage Issues
It doesn’t happen often with sturdee DeWalt equipment, but it can happen. Check to see if the cord are damaged and that the outlet is properly grounded. If you’ve checked the valve, the unloader and the switch and the problem still remains, perhaps its time for a pro.
Not fixing a non-shutting-off compressor is a really bad idea. Not only will it keep you on schedule with your projects, but it’ll also make sure your shop are safe.