<VV> A/C Compressor ...Quasi Vair

[FrankCB at aol.com]

All good points, except that I would be surprised  if a refrigerator 
compressor could "pull" a deep enough vacuum to remove nearly  all the air from an A/C 
system.  After all, a regular A/C compressor in a  car is only designed to 
work with suction side pressure of 25 to 45 psiG, so it  seems unlikely that it 
could get close to 0 psiA (MINUS 14.7  psiG)
    I certainly agree that besides  removing non-condensible air (while air 
can be condensed to produce liquid  air, it certainly can't be done in a 
conventional A/C system) which greatly  dilutes the cooling capability of the 
refrigerant, pulling a  "deep" vacuum is also necessary to remove moisture that 
causes  corrosion.  In addition, pulling and HOLDING a "deep" vacuum proves  that 
the system is tight and will not leak out refrigerant after it is put  into 
service.  Nearly all automotive A/C systems will eventually lose  refrigerant 
due to vibration, and seal leakage.  My 1989 Beretta has to  have a 14 oz can of 
R-12 added about every 7 to 8 YEARS to  restore cooling capability.  After 11 
YEARS I just had to add my  first can of 134a to my Trans Sport's A/C to 
restore it.  Our fondly  remembered "Joe Cool" 1966 Corvair eventually had to have 
a can of  R-12 added every 2 WEEKS to maintain it's cooling capability.  Of 
course,  those days, I could get R-12 on sale for 99 cents per can, so it 
wasn't too  painful.<GGG>  And the 38 degree F. air that the Corvair  blew out the 
center vent was better than that of any newer car that I ever  tested.
    But, as usual, I digress.  While  automotive A/C systems eventually 
develop leaks, those A/C systems found in  window cooling units and refrigerators 
have a much longer leak-free  life.  My refrigerator was bought in April 1969 
and is still keeping my ice  cream hard!  While I did have to replace the 
thermostat, the fan, and the  defrost coil, the refrigerant equipment is still the 
original.  This is  undoubtedly due to all metal tubing (no hoses) and the 
fact that the compressor  and driver (electric motor) are permanently sealed in a 
metal  enclosure with NO shaft seals needed on the compressor - unlike the 
A/C  automotive compressors.
    Frank "prefers to repair rather than buy new  stuff" Burkhard
     
 
In a message dated 8/9/2006 9:41:30 AM Eastern Standard Time,  
corvairduval at cox.net writes:

Yes you  should. Moisture is the enemy of A/C systems. At best it forms 
an ice jam  and prevents the flow of refrigerant. At worst it leads to 
corrosion and  non-lubrication of compressor bearings. It is also a non- 
condensable ( I  may have this term wrong) and as such will not act as a 
refrigerant hence  not as much cooling capacity.

Beg, borrow or steal a vacuum pump if you  want your system to operate 
correctly.

In the old days when there  was no ozone warnings and R-12 was cheaaap, 
shade (shady) tree mechanics  would put one pound of R-12 into a system 
to absorb the moisture and then  purge it out quickly and hope the new 
dryer would find the remaining  moisture. But, it is way too expensive 
money and environmentaly to do this  now. Besides, even then it left 
moisture in the system and problems  resulted.

You can always use my vacuum pump source. Look around for a  refrigerator 
being tossed away and remove the compressor. If it runs,  solder two 
fitting on it that will fit your gages. Actually only one  fitting is 
needed, on the suction side. The other side is left open to the  
atmosphere in operation. Just plug both openings when in service as mud  
daubers, etc will build homes in the small tubes. This may not get you  
down to 500 microns (the standard used in commercial HVAC), but it will  
be a good start.

Add the freon to the system while it is still  under vacuum and most of 
the filling can be done without running the  compressor!

We self proclaimed people also suggest rplacing the dryer  every time the 
system  is opened, but one can put a heat lamp on the  dryer while the 
vacuum pump is running to get the silica gel to release  the moisture. 
The silica gel recharges just fine, you replace the dryer to  replace the 
internal filter.

And don't forget to measure the oil  charge to keep the compressor happy.

Who knew it was so much to work on  A/C?

Frank DuVal