Leak Test - Evaporator Core

One of the most difficult leaks to find is in the evaporator core. To leak test the core:

1. Turn the blower fan on to high for 15 or more seconds, then shut it off.
2. Wait 10 minutes.
3. If the blower fan power module or resistor block is accessible, remove it. If not, check the condenser drain tube for moisture. If it is dry, it may be used instead.
4. Insert the leak detector probe into the resistor/relay opening, or blower case drain tube. If the detector goes to a solid alarm, a leak has been found.
5. If possible, with a flashlight visually inspect the core face for evidence of refrigerant oil. Note that on R-134a systems the lubricant is water soluble so no evidence of oil is likely, even with a leak.