Check that the timing marks on the air damper heater housing and cover (A) are aligned. If they are not aligned, loosen the clamping screws and turn the cover.
With the coolant temperature no higher than 10°C and the engine idling, check the operation of the air damper and the high-speed cam by touching the air damper heater housing. The heater housing should heat up shortly after starting the engine. The air damper should open as the automatic transmission temperature rises. After the coolant has heated up, the high-speed idle switch should operate.
If the heater body does not heat up, check the electrical element as follows. Disconnect the heater connector and check the integrity of the wiring and its resistance. The resistance of the heating element should be approximately 6 ohms at a temperature of 20°C. If this is not the case, replace the air automatic damper heater assembly.
(The text of the article was obtained from the website www.mitsubishiman.ru)