Heater Stuck on Hottest Setting Due to Broken Heater Blend Door on Mercury Mountaineer

Problem Description and Possible Solution

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.

Problem Data
RepairPal Verified
Average mileage: 122,717 (15,000–230,000)
14 model years affected: 1997, 1998, 1999, 2000, more2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
110 people reported this problem
Viewing 1 - 20 of 49 comments
Air conditioner ;lows heat on passenger side. Driver side cool.
My heater started making a loud noise and then it finally went out. I replaced the blend door actuator several times but they kept going out. Everytime I put the actuator in the only thing that will works is my heater. So if I unplug the blend door actuator my air conditioning works. If I plug the blend door actuator in the heater works and my air conditional won't. So in order for me to have air I have to unplug my blend door actuator every summer and in order for me to have heat I have to plug my blend door actuator back in everyone winter which means I have to buy a new one every winter. It's so frustrating don't nobody know what's going on or how the fix the problem please help me!!!!!!
Its actually stuck on cold with a click sound
Blender door open on cold side. Not good timing in winter.
heater blend door not working. found broken vacuum line between firewall and engine. Repaired with plastic tape now works fine.
Blender door broke - no heat in front of vehicle
passenger side air conditioner blows hot air.
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.
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
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
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.
No Heat in side Mountaineer.
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.
Hasn't been fixed yet but reading the source of the same problem of my vehicle not blowing hot air, let's me know it's the actuator.
vent door needs replaced
Stays hot on passenger side cold on driver side
Problem with the heater blend actuator. When I want heat only cold air comes out. Makes a clicking sound all the time. I got if fix before and it worked for a while then it started again.
I had this repaired already and now 5 years later I am having to do it again! The first one cost me over $600.00 and now I am having to do it again? Cheap product!
When a/c is running, vents on right side of dash blow hot air while ones on left blow cold air according to setting in use.
My truck is stuck in a.c. with loud clicking noises coming from dash