Air Compressor won't start.

[K72nova]

My air compressor just hums instead of starting, it will sometimes rotate slowly but won't turn all the way over. This just started a few days ago, I replaced both the run, and start capacitor but that hasn't changed anything. I've tried spinning it up by hand and then flipping the switch on to see if that will get it started but I get the same result. I'm not really sure where to go from here. The compressor has been running fine for a couple years up until this point. The first time this happened I hadn't been running the compressor hard, normal usage and it kicked on and just hummed.

This compressor is a quincy 2V41C60VC.

 

[Dagny]

there has to be a start switch or a potential relay to take the start capacitor out of the circuit. Most common is a switch located in the end of the motor opposite the shaft end. The switch opens at about 80 percent of full RPM an closes when it shuts off, take a look at it.

 

[G_P]

there has to be a start switch or a potential relay to take the start capacitor out of the circuit. Most common is a switch located in the end of the motor opposite the shaft end. The switch opens at about 80 percent of full RPM an closes when it shuts off, take a look at it.

Yeah, if the switch is not working, it wont be using the capacitor and it will act just like a bad start cap.
Also, check your unloader valve and check valve. If it has failed the compressor will be trying to start with the pressure of the air in the tank already in the cylinders.

 

[Davefr]

You need to:
1. Remove the belt and determine if it's the motor or excessive load from the compressor.
2. If it's the motor then put a clamp amp meter on the 220VAC and compare it with the nameplate rating. Also check voltage on startup.

It could be the centrifical switch failing the make contact at start up but I doubt it.

Report back

 

[K72nova]

UPDATE: Air Compressor is back up and running, thank you!

First thing I did was removed the belt between the compressor and motor as suggested. This let the motor spin a little faster but not much, and it still hummed, got hot and wouldn’t turn to full power.

Next I checked my amperage and voltage which were both within normal working levels.

Finally I decided that I either needed to take the motor in and have it looked at or just try it myself, after researching shop rates I decided to just bite the bullet and try it myself, I have zero knowledge or experience with electric motors and very little with electrical in general. Anyway I researched how to open the motor up without damaging anything and found what I assume is the start switch that I was told to look in to.

What I found was this connector was somehow out of place, I’m not exactly sure how this can happen under normal operation but like I said, I have zero experience in this field.

I decided to set it back where it belonged and noticed that it was bent near the center…

So I carefully bent it back to where it looked like it should be….

Now the motor runs just fine. I know that this will most likely fail again and that this is probably just a temporary fix until I replace the start switch, but in my research I noted that this is a common fail point in this type of motor. Is there a work around for this? Some type of external starter maybe? When I looked up motor start switch I found a lot of different styles, from what my motor has, to what looked like a heavy duty light switch, I’m really just wondering if there’s something I can do down the road that will take out an easy fail point in this.

Anyway, I appreciate everyone's input and advice. I wouldn’t have been able to get this running again with it. Thanks!

 

[G_P]

I would contact a motor shop. They will likely either have a new switch in stock, or may have a burned out used motor they can snag you a switch from.
I'd love to know how that happened! Never seen a switch fail like that. The ones I've seen go bad had contacts burned up or soldered on wires broken off.

You are looking for a "centrifugal switch" not a motor starter.

 

[marinusdees]

Ask about a sinpac. An electric motor repair man will know. It is a non-mechanical start switch. It is electronic and not cheap, but your problem will be solved for the foreseeable future.

 

[K72nova]

Awesome, thanks!