air compressor breaker pops at 60psi

[Rema1000]

I have a cheap electric air compressor/tank that I got to seat tires onto rims.  It got run fairly regularly over the past few years (every time I checked pressure in the GS tires). It is now popping its built-in circuit breaker when it hits 60psi (it should go up to 120 easily).  If I am using the air, it seems to be able to run forever, filling the tank.  But when I quit using air, the compressor's integrated braker pops as soon as it hits 60psi.  If I wait a few minutes for the breaker to cool down, it can be reset again.

It still works to keep the tires inflated, but I'll need to figure out what's wrong for my next tire change.

Pictures/sounds of the compressor are at (75mbytes):

http://gs500.specialgreen.com/img/compressor.avi

[GeeP]

Hmm...

Sometimes, as an oil-less pump ages, friction builds in the cylinder.  This can cause the breaker to trip before reaching cut out pressure.

Beyond that, it is possible the breaker is defective.  If you have an inductive ammeter, I would measure the draw of the motor while running.  It should increase as the pressure builds.

[sledge]

It could be down to any one of numerous things...... but the first thing to check is that the motor is seeing its full supply voltage.

If the motor turns off when max pressure is reached then trips when it tries to restart I would suspect the unloading valve. If it trips while running I would suspect the check-valve or as Geep says a partial siezure internaly allthough it doesnt sound to be labouring prior to tripping.

The check valve is the Brass coloured part on the side on the receiver that the pipes pass through. Dump all pressure from the receiver then undo the large Hex-head and see if its clogged up with shyte and condensate......its worth a try 

Maybe the motor winding has shorted and burnt out or the run/start capacitor is breaking down as it sees some load and warms up