Mercury Tech Tip: Air Conditioner Blows Warm Air – UnderhoodService
Connect with us
Close Sidebar Panel Open Sidebar Panel

Passenger Compartment

Mercury Tech Tip: Air Conditioner Blows Warm Air

This 1999 Mercury Mountaineer had its door motor and heater door replaced, but the air conditioner still blows warm. Here’s what else it could be.



1999 Mercury Mountaineer, 5.0L



The customer states the air conditioning is blowing warm air.


Confirmed the customer’s complaint and found the air conditioning was blowing warm air from the vents. Connected a scan tool and found code B1249 – Blend Door Failure. Started the vehicle with the air conditioning set to maximum cool and found the air conditioning compressor operated, which verified the air conditioning system was charged and functional.

Used the scan tool to command the temperature door motor on and found the door motor did not respond. Used a multimeter to test for voltage and ground at the door motor while the door motor was being commanded on and found both power and ground were present. Disconnected the door motor harness connector and used fused jumper wires to apply power and ground to the door motor.


Observed the door motor did not respond, which confirmed the door motor was faulty. Removed the door motor for inspection and found the door motor gear and the heater door motor connector were damaged. The heater door motor connector is integrated into the heater door and is replaced as an entire unit.


Replaced the door motor and heater door, cleared codes, performed a road test and verified the vehicle operated properly. The customer’s concern did not return.

Courtesy of Mitchell1 SureTrack Real Fix.

Click to comment