On Mon, 08 Mar 2010 01:04:59 GMT, lid (Sparks
Fergusson) wrote:

PeterD wrote:

Typical small compressors the unloader opens when the pressure switch
activates and shuts off the compressor. This releases all pressure on
the compressor head, allowing the motor to start when pressure drops
down to the cutin PSI.

On this compressor, the check valve/unloader is completely separate
from the pressure switch. The unloader is similar to this one:
http://www.amazon.com/Control-Device...nloader-Check/


The URL above is 'dead'...

This is probably what you are trying to point to:

http://www.amazon.com/Control-Device...8055829&sr=8-1


IHMO it has not been said that the motor is stalling! A stalled motor
(called locked rotor) will cause input current to swing sky-high,
usually tripping the breaker, making a hell of a noise, and is very
obvious.

The voltage to the motor is never interrupted during the stop/start
cycle. Above a certain psi (about 95), the motor starts bogging down
and eventually stops. This occurs even if I bypass the pressure switch
and attach the cord directly to the motor leads. Then, after the
unloader vents the pressure, the motor will restart.

So the motor actually stalls, and there are no sounds (humming, etc.)
from it?


Input current does not swing sky-high, though, nor does the breaker
trip, nor is there a hell of a noise. It definitely comes to a dead
stop, though.

A most interesting set of symptoms... Motor stalls to locked rotor, no
significant current draw, odd...

How 'hot' is the motor? Is it possible the thermal cutout is tripping
(at too low a temperature, perhaps?)