A failed heater blend door or actuator can cause the temperature control for the HVAC system to stop working. A clicking sound from the dash area would commonly indicate an actuator fault. If the heater gets stuck on the hottest setting, the heater blend door may be broken requiring replacement of the heater box to repair the issue.Google+
Car Problem Reports
Mercury Mountaineer Heater Stuck on Hottest Setting Due to Broken Heater Blend Door
Mercury Mountaineer Problem
Average Mileage: 123,359 mi (44,000 mi - 227,000 mi)
Visitor, 2005 Mercury Mountaineer, 167,000 mi
Its actually stuck on cold with a click sound
heater blend door not working. found broken vacuum line between firewall and engine. Repaired with plastic tape now works fine.
Visitor, 2001 Mercury Mountaineer
first there was a clicking sound, then the heat was stuck on the hottest setting. have called around town and its looking like $340 plus to fix. This is a very common problem with Fords. If the company knows this, they should fix it for free or discount a repair at the dealership. why keep making cars that are gonna have the same problem.
Visitor, 2003 Mercury Mountaineer, 124,000 mi
Just purchased from local ford dealership, two days later clicking sound in heater.. took into service dept and was told not to worry about it... now two days later I have no heat.. taking in tomorrow to see what they will do for me
Visitor, 2005 Mercury Mountaineer, 182,000 mi
Blender door open on cold side. Not good timing in winter.
Visitor, 2003 Mercury Mountaineer
Blender door broke - no heat in front of vehicle
Visitor, 2003 Mercury Mountaineer, 117,000 mi
clicking when changing to heat, as far as I can tell the blend door actuator gear must have some stripped out teeth on it. The actuater being replaced should fix the problem.
Visitor, 1997 Mercury Mountaineer, 222,500 mi
No Heat in side Mountaineer.
Mine was stuck on heat-no AC-bought aftermarket blend door online-after taking dash out found orig OK, but actuator motor broken.bought one at a national parts place, it wouldn't work, took to shop they replace w/ford actuator-now works, but knob to regulate air flow does not work, will cost another $600 to repair-don't have the $$ to do so
Visitor, 2005 Mercury Mountaineer, 65,000 mi
blend door thumps and has troble changing from warm too cold.not fixed dealer told me it will cost a thousands dollars to fix it.