120VAC 15A motor won't spin up to speed

I forgot to mention that it trips the breaker in 15 seconds or less.

There is no belt, the shaft goes right into the compressor. I can turn it quite eaisly with my hand.

- Mike

I'm thinking starter cap and possibly the run cap since they don't look very pretty. I just have no idea what sympoms a motor suffers from when it has a bad start cap..

I guess I'll check the caps with my esr meter.

- Mike

If those are the correct ratings, possibly. But I'd check the windings with a meter first.

Won't run. Buzzes. Starts up very slowly. Halts and catches fire.

-- _____ _ _ |_ _| | | | | | | __ _ _ __ ___ | |__| | ___ _ __ ___ ___ _ __ | | / _` | '_ ` _ \ | __ |/ _ \| '_ ` _ \ / _ \ '__| _| |_ | (_| | | | | | | | | | | (_) | | | | | | __/ | |_____| \__,_|_| |_| |_| |_| |_|\___/|_| |_| |_|\___|_| __ ____ / _| | _ \ ___ | |_ | |_) | ___ _ __ __ _ / _ \| _| | _ < / _ \| '__/ _` | | (_) | | | |_) | (_) | | | (_| |_ \___/|_| |____/ \___/|_| \__, (_) __/ | |___/

hmm.. sounds about right.. ;) Off to go buy some caps tomorrow.

Thanks

- Mike

How do you determine what value cap you need by checking the windings with a meter?

Upon closer inspection there is one 330mfd and one rusty cap that I can't read.

starting winding bad, centrifugal switch bad? starting cap (if you have one) bad ? who knows?

pull the belt off and see if it comes up to speed.

You don't, but if a winding is burned out new caps won't help. BTW, you might have a motor with a start and a run cap. Local distributor may be able to guess at the value - many electrician's meters now will measure the value too.

-- _____ _ _ |_ _| | | | | | | __ _ _ __ ___ | |__| | ___ _ __ ___ ___ _ __ | | / _` | '_ ` _ \ | __ |/ _ \| '_ ` _ \ / _ \ '__| _| |_ | (_| | | | | | | | | | | (_) | | | | | | __/ | |_____| \__,_|_| |_| |_| |_| |_|\___/|_| |_| |_|\___|_| __ ____ / _| | _ \ ___ | |_ | |_) | ___ _ __ __ _ / _ \| _| | _ < / _ \| '__/ _` | | (_) | | | |_) | (_) | | | (_| |_ \___/|_| |____/ \___/|_| \__, (_) __/ | |___/

Remove all load from the motor shaft.

Disconnect everything but the run winding. Spin the rotor by hand and power up the motor. It should come up to speed instantly and run cool.

If this works, the rotor and windings are probably OK.

If it cannot be spun up, buzzes, still catches fire :), one of the windings may be shorted. Another alternative is that the bearings are so shot that it's binding on the stator.

--- sam | Sci.Electronics.Repair FAQ:

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Hi...

You guys are creating flashbacks for me... back to around the time sunshine was invented :)

Anyone else here long enough in the tooth to remember the "growler"? :)

Take care.

Ken

Sure - and the vibrating hacksaw blade.

-- _____ _ _ |_ _| | | | | | | __ _ _ __ ___ | |__| | ___ _ __ ___ ___ _ __ | | / _` | '_ ` _ \ | __ |/ _ \| '_ ` _ \ / _ \ '__| _| |_ | (_| | | | | | | | | | | (_) | | | | | | __/ | |_____| \__,_|_| |_| |_| |_| |_|\___/|_| |_| |_|\___|_| __ ____ / _| | _ \ ___ | |_ | |_) | ___ _ __ __ _ / _ \| _| | _ < / _ \| '__/ _` | | (_) | | | |_) | (_) | | | (_| |_ \___/|_| |____/ \___/|_| \__, (_) __/ | |___/

Hmm.. Well I don't know what you guys are talking about but anyhow a new cap fixed the motor! Thanks evrybody.

Now I found out that the piston ring on the air compressor is bad and it also needs a new piston sleeve. Can you get piston rings and sleves for these things? I dindn't find much on google.

- Mike