Charging your AC system with the small cans of refrigerant

[Josh]

From a Four Seasons Tech Tip document:

Unlike the old days when an R12 system could be 1⁄2 pound on either side of full and still produce cold air, an R134a system is not as forgiving. The acceptable operating window for R134a cooling is about +/- 2oz of full.
If the method of charging R134a is with 12oz cans, then you have to compensate for the amount of refrigerant to an even greater extent. You will still need to allow 2oz for the service hoses and since you can never completely empty a can of refrigerant you will need to allow for an additional 1oz per can.






Read the full document here - AB326.

[Josh]

Just charged up the system in our 1992 38' Champion Europremier after replacing compressor, filter/dryer and TXV Valve and it took 9 of the 12oz cans of R134a. We didn't have any way of knowing how much this system would take so we charged until we got the recommended high side pressure for our 80F outside temperature which is about 200psi. The low side pressure is only about 20 inches of mercury but it should be about 27, not sure what the problem is there.