Evacuate AC system with an air powered vacuum pump?

Can an air powered AC vacuum pump evacuate your car’s AC?

Do air powered AC vacuum pump work?

If you’re contemplating buying an inexpensive air powered AC vacuum pump so you can repair your own AC system, read this post! An air powered AC vacuum pump can work AS LONG AS you pay attention to the pump’s CFM and PSI requirements. Most air powered AC vacuum pumps require at least CONTINUOUS 4.5 CFM at 90 psi to work properly. Don’t think you can fill the tank and run it until the motor kicks in. These vacuum pumps require a continuous supply of air at that CFM and PSI rating the ENTIRE time you’re evacuating the system. Just because your air compressor runs your 5 CFM 1/2” impact wrench doesn’t mean it will run your vacuum pump. That’s because you never run your impact wrench continuously!

Unfortunately, most home/consumer air compressors are rated at around 3CFM @ 90-psi. You really need a heavy duty compressor to provide continuous air for an air powered AC vacuum pump.

Does an air powered AC vacuum pump remove enough moisture?

You evacuate an AC system to remove all air and moisture. Moisture in an AC system causes all kinds of problems. A deep vacuum causes moisture to boil at a lower temperature. However, even if you have the CFM, can an air powered pump actually pull a deep enough vacuum to boil the moisture? Tests show that they don’t, which means you’ll be leaving water in the system. That water will eventually combine with worn oil and refrigerant to form acids that will destroy the system.

Can you use it?

Yes, it will remove the air and some moisture IF you have the properly sized compressor. But it will NOT remove enough moisture to get a professional result. For that you need an electric vacuum pump. Instead of buying an air powered pump, rent a real AC vacuum pump.

© 2018 Rick Muscoplat

All values are at sea level.  Subtract 1 inch for each 1000 ft. above sea level

Opinion…

Venturi pumps are certainly popular with the do-it-yourself mechanic since cost is often times the biggest factor.  I’ll give these pumps some credit since they can remove a substantial amount of air from the system if you have a decent compressor.  Pulling a vacuum on the system is what’s most important in terms of end result to the DIY’er.

Regardless of sales literature, I believe you won’t be able to boil much water out of an automotive system with the vacuum level produced by a venturi pump. I was able to see that by using my micron gauge. I believe air powered a/c vacuum pumps aren’t very well suited for use in an automotive service shop unless you plan on hacking these things apart to make other cool air powered vacuum devices.   We have several very useful items in the shop that derive their power from the guts of a venturi pump.

Summary

If you plan on servicing A/C systems, and want professional results, invest in a good electric vacuum pump.  It’s not uncommon to get ten or more years of service from a good electric pump.  As an option for  the do-it-yourself mechanic, some tool rental companies now rent electric vacuum pumps on a daily or hourly basis.  That may be a better option versus overworking your air compressor for an hour or more, just to get mediocre results.