I have an 80 gal Craftsman air compressor who just shut down, the pressure is dropping, it made a smoke smell and it blew my circuit breaker. I tried starting my circuit breaker but it kept flipping off. I unplugged the compressor and I got the power back. The compressor has oil recently changed, it is fairly new. What could have happened?

It sounds like the motor is being overworked. This could be caused by several things:
- No or low oil in the pump crankcase. Take the belt off the pump and try turning it by hand. Except for needing a little more effort to get over the compression stroke, it should turn smothly and fairly easily.
- Try turning the motor by hand. It should turn very easily with no side to side or end to end play in the armature shaft. If not the bearing(s) may be damaged.
- If the compressor starts up OK with no compressed air in the tank, shuts down at the proper pressure, then has a hard time restarting when the pressure drops to the point where the motor tries to restart and fill the tank, you have a broken tank check valve.
- The capacitor(s) on the motor may be bad which will make it work hard to get started and get very hot. This usually ends with a blown circuit breaker on the motor or line circuit.

Just fixed my compressor. It would start ok when the tank was empty but trip the breaker if it tried to start with pressure. Searched and read about weak caps, or problem with check valve or pressure switch leaving pressure in the pump head, etc. Turned out that the black plastic box which holds the 2 start up caps and is attached to the end of the motor with 2 screws had cracked on the bottom. The black box had tilted out enough that the start up caps switch was not engaging. Pushed on the lower part of the box and it started perfectly. Fixed it for the cost of some 2 part epoxy. Maybe not your fail, but definitely worth checking out first.

Your tank check valve is stuck/broke. It's on the tank end of the line from the pump to the tank. It is supposed to close when the pump stops to keep air in the tank and let the system bleed pressure out of the pump so the motor can start when there is pressure in the tank. The part you need is CAC-437-2 and is available through searspartsdirect.com.

Hi dtsorrell...

If your somewhat of a mechanic/electrician then you can by-pass the pressure switch by hooking the color coded motor wires together with the incoming color coded wires from your power cord in the proper order.
Plug it in and then check to see if it blows the breaker again, if it does then it is your motor that is faulty.
Please take time to rate me.

The problem is lilkely the check valve between the compressor and the tank -- it is alowing pressure to build from tank to compressor preventing the compressor from turning over. Clean, maybe replace, check valve...

Charlie

Most likely it is the unloader valve. This is inline with the air filltube from compressor to tank. Somestimes the unloader valve is screwed into the tank and air tube is attached to it. This device takes the pressure out of the tube so the compressor can start without the back pressure from in the tank. Other possibility, the start capacitors of the motor. The capacitors must give a kickstart upon startup or the motor will just hum for a couple seconds and overload the breaker. A tempoary solution is to turn off the power to compressor when it reaches 120psi, then allow the pressure to drop to 40 or less, then turn power on and mostlikey compressor will start with a load of 40psi or less. It is a nuisance but it works until you replace the bad part. Goodluck,Macgivor

If it is an oil type make sure it has oil. If it is the dry type you need a new compressor.

IT SOUNDS LIKE YOUR COMPRESSOR IS NOT UNLOADING WHEN IT SHUTS DOWN. YOU SHOULD HEAR AN AIR RELIEF SOUND TYPICALLY ON THE SIDE OF THE PRESSURE SWITCH WHEN IT SHUTS DOWN. ITS A SMALL VALVE WITH A TIRE VALVE THAT THE LEVER HITS AND RELIEVES THE PRESSURE FROM THE DISCHARGE LINE AND THE TOP OF THE PISTON.

YOUR CHECK VALVE COULD BE BAD LETTING PRESSURE BACK UP BUT IT WOULD BE BLOWING AIR OUT ALL THE TIME WHEN SHUT DOWN.

IF YOU THINK THE VALVE OR SWITCH IS WORKING AND WANT TO CHECK IT, LET THE COMPRESSOR BUILD UP AND SHUT DOWN, LISTEN FOR THE AIR RELIEF,IF IT DOESNT THEN CRACK THE DISCHARGE LINE AND SEE IF THERES ANY PRESSURE, MANUALLY RELIEVE THE PRESSURE THEN USE SOME AIR AND SEE WHAT HAPPENS. REPAIR VALVE ON THE SIDE OR CHANGE PRESSURE SWITCH $30-40.00. HOPE THIS HELPS. PLEASE REPLY. JODY

It sounds like the internal circuit breaker in the motor is heating up and then the breaker trips to shut down the motor. This is the protection so you don't have a fire if the motor burns up. The smell you have is the coils in the motor. Sorry to say that you will need a new motor for this unit. I hope this helps out.

Does this trip on pressure or is it a breaker tripping? If you took off the intake then there is no pressure build up, thus it wouldn't trip the pressure switch. But would at the same time add a load to the motor. First check and make sure motor is wired properly, then check that pressure switch is wired properly and is adjusted to the right pressure. I don't believe that the intake tube would be clogged, it's a straight hole into the tank. But could be a possibility.