Non starting compressor

My 2 year old Clarke single phase single cylinder compressor stopped yesterday and won't restart, either with residual pressure in the tank or no pressure. The pressure relief valve is free. I've had a poke around with the multimeter: fuse is OK and there's continuity right through the on/off switch with the pressure sensor, through the thermal cut out switch to the capacitors. That's the limit of my confidence with mains electrickery, especially with the big capacitors.
Anyone have any thoughts on what to test and how to test it?
Thanks, John

 

Is there oil in it?
Is the fuse blown?

 

Fuse is OK, oil in compressor. Hoping to avoid buying a new 3hp motor

 

Compressor turns easily enough. No sign of a twitch from the motor.

 

Is there power at the socket? Has the main fuse tripped?

 

Power's there, tell tale lights on double socket both on and both sockets live.

 

Can you not get to the wiring at the motor to check 240v there with a multi meter? If you’ve got power there and the motor turns freely it’s gona be an internal motor issue.

 

I'll give that a go.

 

Also no expert but I have fixed a few motors, if you can its worth going beyond the big external capacitor and checking continuity across the windings. If you are lucky it could be brushes on slip rings and another thing I have discovered is that there is often a thermal cutout switch between the supply and one of the brushes. Klixon is the type I replaced (see photo) they should reset but mine on a washing machine was not playing and when replaced with another from a donor motor all was fine. Its a pity to scrap a big bit of technology for such a small part as a brush or thermal switch. My mantra is keep working on it until fixed or properly broken!!!

 

Found it, I think! No volts across the live side of the on/off/pressure switch. Contact had a high resistance and has overheated and melted a bit of the housing.

 

Thanks for the support everyone!