# Air compressor trouble shooting.



## MrMoonPie (Oct 31, 2015)

Can anyone help me figure out what is wrong with this compressor? It is a Husky 60 gallon. I got it home, wired it up, changed to oil. And turned it on. It really doesn't seem to be running correctly. It is very squeaky sounding, and the motor doesn't seem to want to spin up to 100% rpm. The rpms seem to be oscillating. It also occasionally sparks. Is this a fixable problem? I am sorry if this is very vague, electric motors are not my strong point. And this is my first large compressor. 

Here is a video of it "in action"







Thank you for the help.


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## Osviur (Sep 7, 2015)

*Motor overload*

Hello MrMoonPie,

Your video reveals clearly that the motor is unable to reach full speed without the startrting capacitors help. Let me explain.

A single phase motor needs the help of a capacitor to start running. At approx. 75 % of full speed RPMs, a centrifugal device, installed at the rear of the motor, cuts off the current to the cap or caps ( 2 in your case. Those cylinders mounted over the motor ) creating a visible spark. At this point the motor has enough torque to continue accelerating up to the nominal speed (1740 or 3540 RPM for 60 cycles per second or Hertz Hz). During this start up time, motor current is very high, 6 or 7 times the nominal, but it takes only a few seconds (1-3), not enough to overheat the windings.

If the load applied to the motor shaft is too much, when the centrifugal switch opens there is not enough torque to overcome the load and the speed decreases, closing again the centrifugal contacts increasing the torque and cycling in this way and overheating the motor. To prevent damage it, there is always a protecting device like a thermo magnetic circuit breaker or a simple fuse, that opens the circuit and cut the overcurrent.

The mechanical overload may be, in this case, the compressor or pump, that in this case is operating against an empty air tank (0 PSI),and assuming that there are not restrictions in the air flow from the discharge coupling to the tank, via the check valve, or the motor itself, due to worn out ball bearings.

To determine where is the problem, take the belt out (unplug before the compressor from the outlet) and turn by hand the motor it must turn freely. Move the motor pulley up and down, to check for excesive playing or scartch sounds. If everyhing is ok, check the compressor oil level, then turn the compressor pulley half a turn CW and half a turn CCW. There must be a moderate resistance and the sound of the air valves opening with the pass of the air displaced by the pistons.

If all is ok, connect the plug to the outlet and observe the motor running alone, it must accelerate fast, run smoothly, with very little noise, maintaining full speed without variations.

Throug this checkings you must find something abnormal that is braking the motor. I hope this guide will be useful to find the problem.

Good luck!


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