Leak Test - Evaporator Core

One of the most difficult leaks to find is in the evaporator core because the core is encapsulated into a closed module, and due to its inaccessibility to leak detector devices. To leak test the core:

1. Turn the blower fan on to high for 15 seconds then shut it off.
2. Wait 10 minutes.
3. Remove the blower motor or blower resistor.
4. Insert the leak detector probe into the opening. If the detector goes to a solid alarm, this indicates a leak.
5. If possible, with a flashlight visually inspect the core face for evidence of refrigerant oil.