Adding R134A to the AC system

[Donald]

Does anyone worry about the slight about of air that is in a AC high/low manifold when you connect up the high and low pressure sides and then add R134A?

Even if you get a can of R134A and a 8" hose and low pressure adapter, there is a tiny amount of air in that hose that I assume gets pushed into your AC system?

Or do I worry too much about unimportant things.

 

[punisher]

I always worried about it. I crack the low side fitting on the manifold to at least bleed the charge hose. If you have pressure in the system as well as the charge hose (a cylinder/can attached) then it is possible to completely bleed the gauges and hoses before filling/topping a system. Old style R-12 always got bled before hookup.

 

[mechtech]

It is very important to bleed your hoses, before connnecting them to your car. Air , and especially moisture, will most certainly cause a decrease in AC performance.
This is standard practice.

 

[Kestas]

Yes, you should worry about it. All instructions I've ever read require cracking the valve open just a bit for a short while to displace the air in the hoses with refrigerant. All these "little things" add up to a job well done.

 

[Donald]

How about if you use one of those short hoses that only has a low pressure fitting a gauge and can tapper valve. Not sure how one would purge that short hose.

 

[Kestas]

Same as any hose, just less air to displace. Or conversely, less air to worry about if you don't purge the short hose.

 

[Schmoe]

Take some needle nose pliers and pinch the middle valve on the fill end after turning the feed line on and then purge away.