Some time ago Tom wrote in with a question about why his Husky Pro air compressor motor won’t start? Little response was offered by the visitors to this site then, so I thought we’d ad a bit of information here if you have the similar air compressor and the motor will not start.
This is a Husky Pro compressor with an 80 gallon upright tank and a dual stage pump.
The Husky compressor motor that wouldn’t start is a WEG brand (www.weg.net), and was a 4 HP unit. This motor came equipped with both a “start” and a “run” capacitor which you can see in the photo below as the two “bumps” on the top of the motor. Those “bumps” are the capacitor covers.
Tom also said that he bought this as a used air compressor. When he examined it the owner started it up during the demo. It started slowly, but started.
The fact that the Husky Pro started slowly when Tom was looking at it before buying would suggest there were some issues. That may have suggested a pump seizing issue, a blockage of the air path between the cylinders or down to the tank, or a motor problem.
An early step may have been to remove the belt and try to turn the pump sheave by hand to try a feel any binding or lockup. It should turn reasonably easy, and that may give a good indication as whether the pump may be he problem.
If turning the pump sheave gives the impression of binding or locking up, that may point to mechanical binding or valve issues in the pump heads or in the valves themselves. If the results suggest the pump may be the issue, it’s likely time to remove the initial pump head cover and have a look at the valves within. It may be necessary to replace the gaskets as they may get damaged in the removal and reassembly process.
If all looks good remove the head cover from the second cylinder and perform the same examination, with careful checking of the intake valve that controls the intake air from the first stage, and then examine the high pressure valve to be sure they are not the issue.
If all seems OK, then check the tank check valve. Make sure it allows free flow of air from the pump head to the tank.
If that’s all OK, it’s time to look at the motor.
With the belt still off start the compressor motor. Did the motor start? Was there any sluggishness or slow starting?
A check of both capacitors would be next. Here’s a page about how to test compressor motor capacitors.
Last, if the caps check out, then that likely points to the motor itself being the problem, and a motor check will likely require taking the motor to a rebuild testing house and asking them to check it out thoroughly, particularly with a heavy load test.
Good luck, and let us know what you find if you have to go through this.