A car air conditioning system is sealed, so refrigerant should not disappear quickly. If the system becomes low again soon after a regas, there is probably a leak or a failed component.
Leak testing can involve pressure readings, visual checks, UV dye, electronic leak detection or a vacuum test, depending on the system and the fault. The aim is to find why the refrigerant level dropped before fresh refrigerant is wasted.
A leaking system may involve:
- A cracked or damaged hose
- A pinhole leak in the condenser
- An evaporator leak inside the dash
- Damage from a previous repair
- Corrosion or impact damage
Leak testing is also an environmental and safety issue. R134a and other fluorocarbon refrigerants should be recovered and handled correctly, not released into the air.