Evaporator Core

One of the most difficult leaks to find is a leak in the evaporator core. Perform the following steps in order to leak test the evaporator core:
1. Turn the blower fan to the HIGH position for 15 seconds or more.
Shut the blower fan off.
2. Wait for 10 minutes.
3. Remove the following components, if the components are accessible:
^ The blower fan power module
^ The resistor block
4. If the above components are not removable, inspect the condenser drain tube for moisture. If the condenser drain tube is dry, use the condenser drain tube instead.
5. Insert the leak detector probe into the power resistor/relay block opening if you removed the power resistor/relay block.
If you did not remove this component, insert the leak detector probe into the drain tube.
If the detector goes to a solid alarm, you have found a leak.
6. Use a flashlight to visually inspect the core face for evidence of refrigerant oil.
Note that on Refrigerant-134a systems the lubricant is water-soluble, so no evidence of oil is likely, even if there is a leak.