Aircompressor motor question

[yimbo]

I replaced the motor on my 60 gal. 2 stage compressor about a year and a half ago and I noticed recntly it wasn't comming on. I checked the power all the way up to the back side of the motor and it was good. An electrician friend check it out and couldn't find anything wrong, everything checked as it should so he put a pigtail on and it fired right up. Took it home put it back on my compressor and it worked fine for about 2 months and it has stoped again.
The switch works because there is power on the outgoing side up to the motor. Any ideas? Thanks in advance.

 

[larry_g]

I would start by checking each and every connection. If this is a dual voltage motor it could be a loose wirenut or connection on the terminal board.. depending on style. If it is a capstart motor does it hum or give any indication that it is doing something? Is it in a dirty environment that could be allowing **** into the start switch? I'm assuming a you have a 120/240 vac motor. Are you confirming voltage at the motor or the output of the switch? could be a intermittent wire tween the switch and the motor. Is this a consistant no run or just an intermittent problem? If intermittent could be contacts in the pressure switch.

lg
no neat sig line

 

[yimbo]

Motor is a capstart and it doesn't hum, even tapping on it with a mallet doesn't work. Once it quites running it never started agian until it was dissasembled and put back together then it ran for couple months and has now been dissabled for 2 months. Motor's not hot, no smell of windings. When I checked the power the 1st. time I removed the cover at the back of the motor and checked the screws holding the wires, had power. Motor is only 1 1/2 years old. Haven't been working in my garage much this last time it was running so environment was pretty clean. Talked to a motor repair shop the 1st time and all he said was it's probably shot and I can sell you a new motor for about $600. so I now going to him won't do any good he wants to sell me a motor. I'm not much good at electrical so I'm at a lose. Thanks.

 

[Vicegrip]

Short of replacing the motor you can Check the centrifugal start switch if it has one. Most single phase motors in this duty range have them. The contacts can get crusty and sooted up and loose conductivity. It is most often on the opp end of the motor from the pulley.
You will need to pull the bell housing off the end of the motor to inspect. if it is crudded up you can gently clean the contacts with a fine file. Don't use sand paper, it can leave grit in the contact surface. Test the operation of the switch for stickiness. If the contacts are sooted or burned a bit you need to check why. A cap can be bad or going bad and cause arcing. cleaning the contacts is sometimes a short term fix and the contact surface gets cut down through the coatings that are applied to resist the arcs during startup.

 

[-JP]

I will back-up Vicegrip and say it is probably your speed switch based on your descriptions. Doubt if it is a bad cap being only 1-1/2 years old.

Cooling air on fan cooled motors enters through vents where the speed switch is located and they can get coated with crud if the motor is in a dirty environment. Cleaning or replacing the speed switch is pretty easy.

JP

 

[nehog]

When it won't start, is it totally dead, or does it hum/buzz? If the former, a broken wire, or loose terminal is likely the problem. The latter, a run switch (as Vicegrip says) can do it, or a bad connection to the start capacitor.