Compressor motor problem- Smoking capacitors

[Dr.HairyOlds]

So here’s the background:

Recently bought a nice Rol-Air 5hp compressor used from a business. It has a 5hp Leeson motor. Worked fine until one nice day I was airing out the shop. It was pretty damp and when a turned it on, it sparked some and kicked the breaker. I let it sit for a day or so and dry out. Fired it up and it was working fine again.

The other day I turned it on and it shut down within a few seconds. I smelled a little something so I tore down the motor. I’m no electrical expert, but I didn’t see any obvious burn marks or flaws. So I cleaned it up and reassembled it. Turned it on and it did the same thing. Found the source of the warmth. Looks like one of the capacitors went. Started leaking oil out of it, too.

So I got a replacement capacitor, put it in and tried it. It immediately smoked the new capacitor. I shut it down since it was leaking, which caused some smoke. Now I am puzzled. Any ideas?

Of course I just sold my old craftsman oil less and have a car w/ a flat. Figures

 

[Bob C]

Winding shorted to ground. Bad Contact switch and most likely points arced together. If wired in series, a bad run cap.

 

[Gary S]

When I have a problem like that, I take the motor to my local electric motor repair shop. They test it and let me know fast what it needs.

 

[Dr.HairyOlds]

Thanks Bob. I think that puts me on the right track.

Like I said, I took the motor apart but didn't really know what I was looking at. Now I know that I saw both a centrifugal and stationary contact switch. In searching the web after your post, I found a great trouble shooting guide from Leeson



Quote:
Starting switch may be defective, preventing the motor from coming out of start winding.

The stationary switch looked a little rough. I'll get the info I need to get a replacement and try again.

 

[SGKent]

if the motor has a standard mount, it may be cheaper to buy a new motor. Seems that one will have 1/2 the cost of a new one in the old one before they realize it - and still have it not work. Bearings, bearing plate, gas and time to locate the right switch, electrical parts that don't fit and can't be returned, on and on.

 

[napalmv8]

Try to open motor and get access to centrifugal switch. May be it is possible to repair the switch without replacing it

 

[MikeTHIS]

I'd suggest Mega Ohming the compressor to determine it the is a problem with the start windings.

Unfortunately you'd need to know the motor rating of the windings which may, or may not be listed on the electrical name plate.

I'd also check your voltage because if its out of spec it will increase the starting amperage.

Another suggestion would be the installation of a hard start kit. It's like a "super charger" that gives the motor extra boost on start to overcome amperage issues.

If your uncomfortable with these type of repairs, a local appliance mechanic can easily fix this.