Tools, Sharpening and Power Machinery - air compressor trips breaker upon starting

i have a craftsman a.c. that is about 4 years old. i went to use it about a month ago and it would not run. as soon as i turn it on to fill it trips out the breaker. i tried moving it to outlets on other breakers and it does the same thing. any advice as to what to look for would be greatly appreciated. not very familiar with this type of equipment. also i believe it is about a 31 or so gallon approximately 5 or 5.5 h.p. horizontal.

I moved this thread here, so you might get better advice.

I would think you have either a short in the switch (could be in the pressure switch too) or in the motor. If the motor hums a second or two before tripping the breaker, I would suspect the pump.

Can you tell us exactly what model you have and what is the voltage and amperage of the motor.
Tha amps and volts can be found on the motor itself.
Also, does it trip the breaker immediately upon turning it on or does it hum for a couple of seconds first?
Is this a belt drive unit and if so can you move the flywheel on the compressor? (Make sure it is unplugged first when trying it.)

72chev -- here are a couple ideas from my recent troubles with my craftsman compressor. Something is probably adding friction to the piston -- maybe rust etc. Take the covers off and turn the fan manually and see if there is a lot of resistance. If there is mild resistance than I suggest you remove the tube from the compressor to the tank and try starting it and running for a while. It may take a couple tries to get it going. It should then free up and allow you to start it with the tube back in place. I assume there is no pressure in the tank when you try to start it. If there is pressure in the tank when you are trying to start it, there is a good chance either the check valve is frozen open or the tube unloader valve is not releasing the pressure in the main line. Last, you cannot run these compressors with an extension cord. They have to pretty much be on a outlet that is close to the breaker box and not have anyhting else on the line. Good Luck.

model # of the air compressor is 919.167340, 33 gallon, 6h.p.
motor is ser 2h01, 3450 rpm.115 v, 60h, type k, sf 1.0, ph 1, fr56z, it also says time cont. it is an a.o. smith ser k56a67823, serial # on compressor is 2102124685. turns manually with no resistance, it does trip the breaker immediately upon starting. my uncle seems to think it is the motor. how can i be sure of this?

We once bought a new Campbell Hausfield and it did the same thing. After we got our fill of diagnosing the problem in vain, I took the motor apart and found an extra drive key stuck to the magnet in the armature, which lodged against the frame whenever it started, and bound the motor and tripped the breaker. However, I was getting the telltale stall when energized.
Yours sounds like an electrical problem more than mechanical.
Another thing I did was to convert it to 240 volts at the peckerhead and change the plug.

There is a parts list for your compressor here:

http://www3.sears.com/Paul/document_search.asp?bnd_id=0247&prd_typ_id=0703000&model_num=919167340&doc_id=&model_desc=AIR%20COMPRESSOR&

A motor shop would be the one to confirm for sure the motor is gone.

If you have and can use an ohm meter you could do a basic test yourself.
You could try to see if the motor windings are shorted to ground.
Disconnect the motor and with the meter set to the highest ohm setting probe the case of the motor and each of the motor leads in turn.
If you get any reading then the motor windings are shorted to ground.
If not set the meter for a low reading and probe the two motor leads.
Should be in the range of 100 ohms or so. If zero while on a low setting then the motor is shorted.

A simple test that sometimes gives you a clue is to smell the motor end of the pump to see if you can detect a burnt odor.

72chev -- try one more thing -- take the cover off the pressure switch and see if it runs with the cover off. If it does, the cover may be putting side pressure on the contacts and the fix is to put the cover on somewhat looser. Also check the contacts and make sure they are clean and actually making contact and not binding. The contact design on these switches is marginal at best. I know you already know this however as a reminder, please make sure you check this with the unit unplugged. Last -- do you own a 72 chevy if so what model, engine etc. I have a 66.

thanks guys i will try these few tips you've told me. i do have the cover off the pressure switch and it will not run with it off either and the contacts look good and clean. yes i do own a 72 chevelle ss with a 454 motor, 4 speed, lemans blue. that is my pride and joy.

72Chev -- Here is one last thing to try if you have not -- try bypassing the pressure switch and see if the motor runs without tripping the breaker. The 72 Chevelle sounds like a great car. I assume it is dark Blue which is an outstanding color. I have one of those plastic 66 cars -- a coupe - it is a big block 427/425.

Here's something I am suprised no one has mentioned..

Hit the motor housing with a _rubber_ mallet a few times around the casing.

If it has surface rust holding the armeture, the mallet should break it loose.

This method has worked for me on motors that haven't been ran in a while and are exposed to the elements (like pool pumps).

i did try bypassing the pressure switch and it still tripped the breaker, i will try the rubber mallet trick next. actually the 72 is more of an aqua or teal color...white top..black interior..i have one of those models also. the 72 and darker blue..

actually the 72 is more of an aqua or teal color...white top..black interior..i have one of those models also. the 72 and darker blue..

Not sure i have ever seen one in that color -- I have seen a kind of silver blue and nassau blue but not teal. Is it a rare color ?? Wow a corvette too -- what else do you have ??

Not sure i have ever seen one in that color -- I have seen a kind of silver blue and nassau blue but not teal. Is it a rare color ?? Wow a corvette too -- what else do you have ??

no no, it is a 72 corvette color.. don't have a vette, only like the old old vettes. i ment i have one of those plastic models also it is the dark blue. only have one classic car..it is enough.$$ add up quick.