Volkswagen Golf Mk7 Service & Repair Manual: Detecting leaks

External damage can cause leaks in the refrigerant circuit. Because a small leak will involve only small quantities of refrigerant, leaks should be checked for using an electronic leak detector or by introducing a leak detection additive to the refrigerant circuit. Electronic leak detectors can detect leakage rates of less than 5 grams loss of refrigerant per year. The leak detector should be specific to the composition of the particular refrigerant in use. For example, a leak detector for R12 refrigerant is not appropriate for R134a refrigerant because R134a refrigerant has no chlorine atoms to which the lead detector responds.)