On Sun, 28 Nov 2004 11:45:44 -0500, Bob Engelhardt wrote:

I have a similar situation: the compressor has a difficult time starting
and if it's cold, it won't start at all (labors slowly along until the
breaker trips). The only way that it starts instantly is if the outlet
from the compressor head is disconnected. I *definitely* ruled out the
unloader and the check valve. BTW - the check valve cannot be the problem
if the unloader is working: the unloader drains the pressure between the
compressor and the check valve. A bad check valve would just bleed down
the tank through the unloader. The capacitors are ok on a go/no-go basis
(not short or open).

The unloader doesn't stay open after cutoff. It opens to relieve head
pressure and then closes. So a leaking check valve will re-pressurize the
compressor.

When I saw "habbi's" post I checked my centrifugal switch. It was
pitted, so I cleaned it. When I tried it, I noticed a lot of arcing
during start (it still didn't start right up). It was "hunting": at
stop the switch is closed and it gets *almost* to speed and the switch
opens. Which causes it to slow and re-close the switch. This repeats.
When it has warmed up it doesn't do it.

The start switch should not be doing "a lot of arcing during start". At
most there might be a brief spark as the switch opens. A bad start cap
would not allow the motor to reach a high enough speed while on the start
windings to be able to run and cause this sort of cycling between the
start and run windings.

So, at cold the load is too much for the motor to get to speed before
the centrifugal switch opens. Which means: 1. The switch needs to be
adjusted or replaced (adjustment seems highly problematical), 2. The
compressor is putting too much of a load on the motor (can it degrade in
some way to increase the load?), 3. The motor has lost starting power
(can the starting cap lose capacity?)

I'd try replacing the start cap. They do weaken with age and are
temperature sensitive, so a dying start cap could cause the symptoms
described. And a for just a few dollars the cap can be eliminated as a
cause. While is possible that the counter balance springs in the start
switch have weakened, allowing it to open early, that's not a likely
failure.

--
The instructions said to use Windows 98 or better, so I installed RedHat.