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jburd964 08-03-2011 07:31 AM

Air Compressor, Motor Capacitors
I think I've torn up my air compressor and electric motor. I'm sure the compressors gone, there isn't any compression when turning it by hand. My question to you is if motor is still attached to motor and it freewheels to does that mean it's go also? I had a air leak in line and I forgot it on. I think the compressor crapped out and the motor possibly ran tell it crapped out too. The 220 volt motor doesn't smell burnt but it want run. I took the inspection covers off pressure switch, cover where power goes to motor and the covers on the capacitors and there is power all the way to everything but no running motor. I know one of the capacitors is for starting up and the other for running. How do it distinguish between the two and trouble shoot if one's bad? Where would it be best to submit a question about rebuilding a air compressor?

a7ecorsair 08-03-2011 08:41 AM

Do you see a red button somewhere on the motor? It would be the overload protection. Most compressor motors have this so look around and when you find it, press it..

J. V. 08-03-2011 11:17 AM

That must have been hard to "tear up" a motor or compressor. Did you do it bare handed or did you use gloves?

jburd964 08-03-2011 12:00 PM

a7ecorsair Forgot to mention that I did press reset.
JV, I only used my man parts and did have welding sleeve pulled over it to keep the sparks under control.

a7ecorsair 08-03-2011 01:05 PM

How many days do you think it ran before dying? You said there is power getting through. Did you measure 240 volts across the two input wires and then 240 volts on the motor side of the contactor?

jburd964 08-03-2011 01:44 PM

That's were the problem lays I'm not real familiar with 220V used in a motor application only house usage. I tested both side of capacitors and they read 120 per, when checked from pole to ground. Never did the total of one pole read 240, which I don't think is possible. Would that be the total of both poles=240 reading that you mention are something different? How can I check each capasitor for functionality? How can I tell which capacitor would be start and which would be run?

a7ecorsair 08-03-2011 02:36 PM

Take the cover off the pressure switch. Be careful while probing.
Find the two wires that bring power to the unit from the wall. Each one should be attached to a screw on the pressure switch. Put your meter on a setting high enough for 240 volts.
Read across the two screws. Don't bother reading to ground. What do you have? You should have 240 regardless of the condition of other thing.
Waiting for reply.

jburd964 08-03-2011 03:39 PM

Checked across poles at pressure switch and both sides read 240. Checked across capasitors and it read 1.___volts are less across them.

a7ecorsair 08-03-2011 04:33 PM


Originally Posted by jburd964 (Post 699649)
Checked across poles at pressure switch and both sides read 240. Checked across capasitors and it read 1.___volts are less across them.

Just so I'm clear on what you saying,
The input is 240 V
The pressure switch output to the motor is 240 V, that is the other two wires connected to the switch.
You can't put your meter leads on the two terminals of a capacitor and get a reading.
Since you verified that you have 240V going to the motor but the motor isn't running, you have a bad motor. Maybe someone that is good with motors can chime in and give you some ideas.

jburd964 08-03-2011 07:03 PM

Not being smart a** But how does power get through a pressure switch to motor mean motor's bad? What is the purpose of the capacitors? The motor doesn't have burnt smell.

a7ecorsair 08-03-2011 09:48 PM

The capacitors are part of the motor, yes they can be replaced separately but they are still part of the motor so if the pressure switch is passing the 240 volt power to the motor leads and the motor is not running then the motor, in general, is bad.
The capacitors are used to help get the motor started and/or to run by creating a phase shift in the current.

CheapCharlie 08-03-2011 10:38 PM

Checking a motor
3 things you can do to check a motor.

1- meggar the motor...since you probably don't have (or have access to) one, you can for now assume the winding insulation is good.

2- check winding resistance-see the nameplate on the motor and you can calculate what the winding resistance should be. Measure with an ohmeter (POWER OFF)

3- check for bearing failure. This would be obvious if the motor was locked solid. Will also trip your breaker if this were the case. Worth a check for noisy bearings though.

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