Refrigerant (A/C Gas)

Older cars use R134a; most newer cars use R1234yf, which has a much lower climate impact. Some electric cars use R744, which is carbon dioxide. The system is sealed and filled with a precise amount, given on a label under the bonnet. A small amount of special oil travels with the refrigerant to lubricate the compressor.

Handling refrigerant requires certified equipment and, in many countries, a certified technician, because releasing it into the air is not allowed.

The refrigerant evaporates in the evaporator and takes heat from the cabin air, then is compressed and condensed outside, where it gives the heat away.

Low refrigerant makes the air conditioning blow warm or only slightly cool air. Because the system is sealed, a low charge means there is a leak. Topping up without finding the leak only helps for a short time; a leak test with dye or an electronic detector finds the cause.