<VV> Refrigerator compressor vacuum pumps

[Jim Simpson]

Rotary refrigerator pumps have been the "darling" of the amateur 
physic world for decades as roughing pumps for high vacuum 
experiments.  For very high vacuum operation, you need to change the 
oil to a low vapor pressure oil, but otherwise they work just fine on 
relatively small volume systems.  Usually one is adequate to get the 
vacuum down to the point where an oil or mercury vapor pump can be 
used, but that's a lot lower than you need for an automobile A/C system.

If you really are concerned, then just hook two in series.

The bottom line is that they will get to very respectable vacuums 
with the major limit being the volume of air they will move.  (Big 
systems, or systems with leaks, need big pumps.  But you really don't 
want any leaks in an A/C system...)

Jim Simpson, '66 Corsa turbo (so no A/C), some-times amateur scientist