Using A/C gauge manifolds
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Le Mans Master
Joined: Sep 2003
Posts: 8,847
Likes: 795
From: Longview Texas
Using A/C gauge manifolds
What is the best procedure for purging air out of all the hoses before adding freon?
I know I can purge the line from the freon can by loosening the hose at the manifold and using can pressure, but do I also need to bleed the air out of the high and low side hoses?
Is it necessary to worry about the high side hose since flow "should" just be toward the manifold? (I assume the high side valve is closed during charging, and only opened to check the pressure?)
I know I can purge the line from the freon can by loosening the hose at the manifold and using can pressure, but do I also need to bleed the air out of the high and low side hoses?
Is it necessary to worry about the high side hose since flow "should" just be toward the manifold? (I assume the high side valve is closed during charging, and only opened to check the pressure?)
Le Mans Master
Joined: Jun 2009
Posts: 6,528
Likes: 752
From: South Dakota
On the manifolds there are 3 hoses.
One is to the low side hose and will be connected to the low side port on the car.
One is to the high side hose and will be connected to the high side port on the car.
One is to the vacuum source or freon/R134a hose.
All three hoses should be evacuated before connecting to the car.
The valves on the manifold connect either the high side or low side to the third hose (vacuum source or freon/R134a), but the high side or low side hoses are directly connected to the car. If they are not purged, the air in the hoses will move into the car's system. There can be some variation in the car's system so that it "breathes" and can pulse back and forth some between the hoses and the system and get air from the hoses into the system.
The high side needs to be closed during charging. If you are using some of the small cans they can explode if you open the high side to the can and then the can sees about 250 psi or more.
Good luck and be careful.
