When I switch on the air-con in my two-year-old Korean car, water drips onto the floor of the front passenger seat. Although my mechanic blew compressed air through the evaporator drain to clear any clogs, the problem still persists. What could be wrong?

As water condensation from the humid air outside passes through the air-con system's evaporator core, which is within the dashboard, water drips off the evaporator to the bottom of the plastic evaporator housing. The water droplets then exit via the evaporator drainage tube.

Your problem is due to a leakage of moisture-rich air around the evaporator core. The air thus delivers condensation further into the ductwork, which is not designed to drain off the condensed liquid, leading to water dripping onto the floor.

To repair this, you have to remove the evaporator and reposition or replace the evaporator seal. This is to ensure that all incoming air passes through the cooling fins of the evaporator core, leaving no pathway for air to bypass the core and reach the ductwork.

Automobile Association of Singapore