On Monday, June 8, 2015 at 1:17:24 PM UTC-4, Terry Coombs wrote:
trader_4 wrote:
On Monday, June 8, 2015 at 12:07:34 PM UTC-4, Boris wrote:
Thought I'd start a new thread.

I spent about five hours yesterday taking apart and cleaning the a/c
condenser. It didn't help.

When I arrived on scene, the a/c was working fine. Cold air was
blowing out of the vents. The refrigerant drier cannister happens
to be located on the small line outside the evaporator. This line
was very slightly warm to the touch. The larger copper line going
into the evaporator was cold to the touch. The outside of the
plenum was also cold (not freezing).

After about 30 minutes, the a/c unit's fan turned off, the furnace
fan remained on, and the evaporator line outside the plenum, and the
plenum, got warmer.

Time to clean the condenser. I turned off the thermostat, pilled
the 40 amp fuse at the a/c unit, and disassembled the side panels,
the fan, and any wiring as necessary. The compressor had an orange
vinyl insulated sort of pull down 'hat' over it. I took that off,
too, to get the compressor specs, if needed, and I put my hand on
top of the compressor. It was hot enough that I couldn't keep my
hand on it for more than a second or so, but not hot enough to cause
immediate burns.

There were lots of leaves in the drip pan, but not much came out of
the condenser. I first vacuumed both sides of the entire consenser,
and there was not much debris at all. I then wetted and sprayed
foam on the outside, and rinsed from both the outside and inside,
until all runoff water was clear. Actually, I was surprised at how
little dust/dirt there was. The only thing that was really dirty
was the temp sensing unit that sits on the small copper line, right
where it enters the compressor. I removed it and cleaned it off
good.

I got it put back together, turned it on. The outside temp was now
100 degrees. The indoor temp was 77, and I called for 66 at the
thermostat. Cool air started coming out, measured at 64 degrees (I
guess the attic ductwork was really hot) and it ran fine for about
40 minutes. Then, warm air came out. The a/c fan stopped. I hand
checked hand temps at the plenum, and it was warming up again.

Crap.

I'm calling another company out for a another look before I replace
anyting major.

I would look at a wiring diagram for the unit and see what
it takes for the condenser fan to stop running. IDK how they
are wired, but my first thought would be that the thermal
protection for the compressor would stop just the compressor,
not the fan too. If that's true, then something else is
wrong, eg bad contactor, that is stopping both the compressor
and the fan......

If the condenser fan stops , the compressor will overheat and shut down too
... try it again , and when the fan turns off check the compressor , if it's
still running replace the fan motor .

--
Snag

That's an excellent observation. He could check for voltage at
the fan when it quits.