Pressure temperature chart or PT chart is one of the most important tool to evaluate system performance or diagnose problems.Technicians can use it along with metering
gauges to check the proper functioning of Air conditioner (AC) Systems .Below you can see the PT charts of most important refrigerants :
Many car manufacturers will not cover your car parts under warranty if you use any refrigerant other than R134A.So just check all the details with your manufacturer before opting for any refrigerant blends other than R134A.
All car models built before 1995 uses R12 as refrigerant for car AC system. Since then R12 is replaced by R134A because of lower GWP. You cannot use R134A in car AC’s deigned for R12 as R134A operates at a much higher pressure.
You have to retrofit your old car AC system to use r134a using below steps .
R134a is the most popular refrigerant to charge the AC systems inside the car.
Keep in mind that you will need to vacuum the car if the AC is discharged completely.
• You need an AC main fold gauge and a vacuum pump.
• AC Main fold gauge has three lines : blue, red and yellow. Connect yellow to vacuum pump, red to large fitting and blue to small fitting in the car.
In 1990′s the most popular choice for car AC refrigerants was R12.It was manufactured by Dupont and marketed as Freon. It was chlorine based (HFC or HYDRO FLUORO CARBON) and has a very high warming potential (8500). It was banned in the 90′s because of its adverse effect on Ozone layer and search for green refrigerants started.
R134a refrigerant replaced R12 for charging Car AC’s as it was effective in cooling and has a 7 times less warming potential (1400) than R12.In recent years ,EPA has announced
• All the vehicle models starting from 2011 has to use a refrigerant with a warming potential of less than 150.
• Starting from 2017 all new vehicles sold will have to meet the low global warming potential requirement.