Automotive A/C Compressor questions

[rover]

You might be able to use an air compressor in this way, but i wouldnt recommend it.

Evacuating a refrigerant system isnt about removing air (non condensibles) from the system, if it were that simple you wouldnt need a vacuum pump at all, purging would get do the job. Nor is it strictly time based. Its about removing moisture. The purpose of evacuation is produce a vacuum deep enough to lower the boiling (evaporating) point of water, to remove it from the system. Moisture is the main killer of refrigerant systems. In older systems, R12 is a chlorine (Cl) based refrigerant, which when mixed with water in the right quantities (H20), becomes HCl, HydroChloric Acid. Not a good thing to have running around the inside of your AC system.
In non chlorinated refrigerant systems, as with chlorinated systems, it can cause problems with freezing at the expansion valve, or orifice.

In order to achieve the evac required, you need to evacuate to at least 500 Torr, or 19.7 inches of mercury, for a minimum or 30 minutes, and i doubt that any venturi system run off an air compressor could get anywhere near that depth of vacuum.

I had an older air compressor with a leaky tank. When I converted it to a vacuum pump, I could pull a FULL vacuum, as much as a commercial evacuator, and hold it indefinitely, boiling out any moisture. I can not understand your reasoning that this is not a good way, my homemade evacuator does EVERYTHING a commercial unit can do, even tho it is bigger and bulkier, but for the difference in cost, I will live with that!!!

[CaptonZap]

I think what he was referring to was one of the vacuum makers that use an air stream over, or past, an orifice. While they will, if engineered correctly, and have high pressure air, produce a "high" vacuum, the ones at Habba Fleight are not good enough for refrigeration work, if you want to do it to industry standards. And they use a lot of air, which is produced by electrical power driving the compressor, which then releases the pressure to produce the vacuum.
It is more efficient to use the electricity to produce the vacuum in the first place. Plus, you can get a higher vacuum that way, if you have a good vacuum pump.
CZ