Charge the air conditioning system with system-safe CO2 and plug the evaporator condensation drain hose. At 160 psi, the CO2 charge is at a higher pressure than the refrigerant in the low side of the system, which is based on ambient temperature.
Thirty to 60 minutes later, the plug is removed from the drain hose and the electronic CO2 detector is held against the drain hose.
If a leak is present, the CO2 will fall to the bottom of the evaporator housing and collect in the condensation drain hose. This CO2 that collected in the condensation drain hose will be sensed and will set off the CO2 alert, making it quite easy to find a leak in the evaporator core or core connections.
Information provided by: Automotive Test Solutions, Inc.
