Re: [DML] A/C problem: compressor is not cycling
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Re: [DML] A/C problem: compressor is not cycling



Your head pressures are still way too high. Pulling a 27" vacuum is
nothing. You need to get into the 500 Torr range to get all the air
and water vapor out. You cannot test for leaks by pulling vacuum. You
are only pulling against 15 PSI atmospheric. Holding a vacuum is no
big deal, it can only show that you can hold against the biggest leaks
and some seals are lousy holding against vacuum but won't leak under
pressure. If you cannot get a hard vacuum get to a shop that can.
Refill with 2.25# of R-12 and then adjust the low pressure switch
until you can get the cycling right. If it won't adjust then replace
it.The system MUST cycle or else you will freeze up the evap coil.
When adjusting the low pressure switch run the fan on high and the
temp all the way to cold. Make sure the evap coil and the condenser
coil are both clean. I am also wondering about your orifice tube. Your
low pressure at idle is too high.
David Teitelbaum
vin 10757 



--- In dmcnews@xxxxxxxxxxxxxxx, Travis Graham <tgraham@...> wrote:
>
> I think this one's solved... for now, at least.  To recap, I had a  
> concern that my A/C system pressures weren't quite right.  I also did  
> not notice my compressor cycling.  I got several suggestions and  
> several pointed to a possible low oil level in my A/C system.
> 
> Last weekend I ran the car with the A/C on for 20 minutes, them  
> immediately reclaimed the R-12, removed the compressor, and drained  
> the mineral oil.  I didn't get much old oil out at all - my system  
> was apparently very low!  I then re-installed with new o-rings all  
> around, added 7 oz of fresh mineral oil, vacuumed the system at 27 in- 
> Hg for 1.5 hours, held that successfully for 1 hour, recharged with  
> 2.25 pounds of R-12, and now I'm getting these pressures:
> 
> ambient temp: 85 deg. F
> rest pressure: 66 psi
> 
> @idle:
> low side: 45.5 psi (was 42 psi)
> high side: 160 psi (was 155 psi)
> 
> @2500 RPM
> low side: 30 psi (was 28 psi)
> high side: 235 psi (was 206 psi)
> 
> @3500 RPM
> low side: 29 psi
> high side: 250 psi
> 
> There were three variables since last time: 1) 0.25 additional pounds  
> of R-12, 2) more oil in the system, and 3) much longer evacuation.   
> The compressor still does not cycle when idling, but I understand  
> that's not a problem in my scenario (hot and outside).  I don't know  
> why the idle low side idle pressure was higher this time around, but  
> the rest of it seems like a step in the right direction.  The output  
> at the vents is colder, especially at idle.  Now I just have to find  
> the leak (if it wasn't any of those o-rings on the compressor) and  
> get that fixed.
> 
> A big thanks to David Teitelbaum, Tom Niemczewski, and Harold  
> McElraft for their on and off-line advice.
> 
> Travis Graham
>









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