Modern vehicle Air-Conditioning systems are designed to work efficiently with a very specific refrigerant charge. Some Systems now have a significantly smaller quantity of refrigerant than we are used to seeing and this has implications on how systems are serviced.
For example various refrigerant Charge Charts show AU Falcons (1999-2002) at 800-900 Grams of refrigerant whereas the series 2 FG Falcon from 2013 on is listed as only 430-500 Grams. 40 grams extra refrigerant in a system that only holds 400 is a 10% overcharge!
As Covered in a presentation at the VASA conference 2019, there are a number of precautions to avoid overcharge situations.
* The Correct Refrigerant levels must be adhered to.
* The practice of pulling refrigerant from the charging lines at the completion of the recharge process into the system via the low side once the system is full will overcharge a system so must not be used. The Couplers should be shut off before being removed leaving refrigerant in the lines.
* The old practice of adding 30 grams of Oil to a system at every service will potentially cause poor operation of the system by:
• Overcharging and causing high head pressure. • Causing poor heat transfer from the Condenser to passing air. • Oil Slugging and subsequent Compressor failure. • Any Oil removed from a system on servicing must be measured and the equivalent amount and correct type of oil should be replaced.