Can someone explain how pulling a vacuum works on a closed AC system? I would think if no air can get in, how can it get vacuumed out?

Robert

 

You don’t pull vacuum on a closed system. Only on one that has been opened to replace parts. Pulling a vacuum serves 2 purposes. One is to remove any moisture from the system. 2 is to use the vacuum to check for leaks after a repair.

 

Buy a bottle of water, drink most of the water and then wrap your lips tightly around the opening and suck on the bottle. If the plastic is thin enough it will start collapsing.
You are in effect trying to create a vacuum.
In the A/C system, when the vacuum gets to 500 microns, water turns to vapor and also gets sucked out with any any all other gases (air).
Then you are ready to fill with refrigerant.

 

Thanks for the info, I was always a bit confused on how that removed .moisture.

Robert

 

I’m always amazed at the process.

 

By pulling a vacuum on the system it makes any water moisture in the system vaporize or “boil off”and out of the system. And as stated earlier in posts,….check for leaks, i.e. hold the vacuum over time…usually 30 min…..also if system has nothing in it you get a better refrigerant charge. …and with no moisture, water can not freeze in the expansion valve or orifice tube (where the compressed refrigerant is a liquid is allowed to expand into a gas….this is known as a phase change and it absorbs heat. That is why some gases happen to work very well as refrigerants. The best I know of is propane, but since it is very flammable you MUST NOT have any leaks. It is however about 30% more efficient than R-134A…and about 12% more efficient than R-12…and non-ozone depleating)

 

Thanks for the additional info. I think I will hold off on switching to propane as my AC refrigerant though.

Robert

 

Understand. And our hhr a/c has always worked very well on R-134a.
I forgot to mention before…..runs a lot lower high side pressure with the propane refrig.

 

Propane coolant sounds pretty dangerous. Get a few "No smoking or open flames within 50 feet of vehicle" signs to post.

 

Refrigerant, not coolant….and your not suppose to have any leak. Really its such a small amount there isnt that much danger involved. Not nearly as much as gasoline. Go to Dura-Cool’s web site and read about it