compressor problems

[phat46]

When I turn my compressor on it sounds like the motor is really laboring and it will blow a 30 amp fuse.  It has done this occassionally for a while, but now it is constant, rendering the compressor useless. I thought maybe the check valve wasn't working and it was pumping against tank pressure. Even with the pipe to the tank dissconnected it acts the same. Now I am thinking maybe the capacitor is bad. Does anyone know how to check this?

[GPster]

OK, I'm going back years ago through my memory and here it is. There are 2 types of capacitors as I remember "Start " and "Run" . The start capacitor is wired through the start circit of the motor (centrifigal mechanism or a relay) so that it is only in the circit when the motor is starting. Normally these capacitors have a rating in MFD's that cover a range (like 130 - 180 etc.) and they used to be cylindrical in shape and had a bakelite outer skin. Usally when they go bad there is a little hole on the end with the terminals and it looks a little blown or there is no continuity between the terminals, BE CAREFULL, IF THEY ARE NOT BLOWN THEY STORE ELECTRICITY AND WILL SHOCK YOU.  Always short them out accross the terminals and to ground with the power OFF before checking them.  My memory of run capacitors is mostly that they seem to provide a connection between the run windings and the start windings so that the run circithas some help to handle the load by the start windings. In some motors (easy start) there is no starting mechanism. This connection with the capacitor to give a start circit a little jolt gets things under way. Most of the run capacitor in my memory where of a straight, lower MFD rating (like 25mfd) and had a metal shell and appeared like an oval cylinder. A lot of times whenthey where bad they swelled or the terminals shorted to the shell and therefore to ground by way of the mounting. These things can shock you too but the metal case gounds and discharges them a lot of the time. Remember to turn the power off. If the motor doesn't come up to the speed necessary to un-couple the syntrifical starting of the motor then it will blow a fuse because the start windings and the run windings of the motor are pulling power too long. I hope for your sake in testing the compressor is belt-drive. Un-hook the belts after checking the capacitors and try to start the motor.  If it still labors to start with no load then it's probably in the motor and circit. If it snaps to then there is probably a mechanical drag in the compressor. I would have checked the check valve first too. GPster

[MrMopar64]

When I turn my compressor on it sounds like the motor is really laboring and it will blow a 30 amp fuse.  It has done this occassionally for a while, but now it is constant, rendering the compressor useless. I thought maybe the check valve wasn't working and it was pumping against tank pressure. Even with the pipe to the tank dissconnected it acts the same. Now I am thinking maybe the capacitor is bad. Does anyone know how to check this?

Sounds to me like it might be bearings.... take the belts off and turn them both by hand and make sure they are free

MM64  

[Mikej]

It is probably the cap. Its fairly common. You could take it to a appliance or TV repair shop. They should be able test it. OR............make a jumper cord ( 2 clips on an old 110 volt cord). Unhook cap, put clips on the terminals, plug the cord in, let the cap charge for a second, unplug the cord and then short across the blades of the plug. It should spark. I assume no liability for this procedure.

[Rayvyn]

When I turn my compressor on it sounds like the motor is really laboring and it will blow a 30 amp fuse.  It has done this occassionally for a while, but now it is constant, rendering the compressor useless. I thought maybe the check valve wasn't working and it was pumping against tank pressure. Even with the pipe to the tank dissconnected it acts the same. Now I am thinking maybe the capacitor is bad. Does anyone know how to check this?

My Coleman 30 gallon upright did the same thing, only it turned out the piston and ring were shot and the diaphragm was in pieces. A coupla new parts, and it's been running like a champ for 2 years now.

[phat46]

I guess i should have mentioned that it is a direct drive cheap-o-P.O.S. oil-less Cambell-Hausfield. I really need a new one, a good one. But i have some parts to paint and I wanted to do it right away. i guess i could buy a new one a quickly as fixing this one. Thanks, I'm not too sure i want to mess the the capicitor anyway