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1997-2001 Mercury Mountaineer - Heat and AC Blend Door Replacement Parts

The HeaterTreater replaces the plastic blend door with steel. Replacing the existing door with another plastic door is at best a stop-gap solution. The failure is a result of excessive forces in the operation of the blend door. Modifying the top or bottom axle contact points will further weaken the system and result in faster failure of plastic components.

Replacing the plastic door is only solving the symptoms of the problem. The same system design problem that caused the failure in the first place WILL re-occur over time. The HeaterTreater attacks the root cause of the failure by constructing hardware that is designed to meet the rigors of normal operation of the HVAC system, and last for the life of the automobile.  The kit includes detailed instructions and all hardware required to complete the fix, including dremel bits and metal tape to seal the cut.

This is a kit to do a complete repair on the blend door malfunction that is common to 96-2001 Ford Mountaineers.   Every Mountaineer in this range either has, or will have, this common failure.  The pictures show the hardware provided for the fix.  All work is done through the glove compartment opening and a Dremel cut in the bottom of the heater box...no removal of the dash panel or evacuating the AC system and draining the radiator.  Once completed, the alterations are under the dash panel in the foot area and are not visible.  The work to install the fix is relatively simple and can be accomplished by the average shade tree mechanic. The work could easily be done by any local independent garage. Product returns are accepted within three weeks for a full refund(minus shipping).

The standard fix for the blend door failure is to remove the heater box and replace the plastic door. If the instructions with other fixes start out with "remove the heater box or dash panel", be ready for considerable work. Removal of the box requires removing the dash panel, evacuating and disconnecting the AC compressor, draining and disconnecting the heater hoses. Fixing the door is relatively easy, but the labor(and cost) of getting to the door makes this a time consuming and expensive job. The HeaterTreater avoids the hard work by providing a kit that allows the repair to be done with superior components without having to disassemble the automobile. 1hr work vs 8-14 hours of work, and no specialized mechanical skills required.

  
The Problem:

-  The Mountaineer is built with a Blend Door to control the heater and AC function.  The blend door controls air flowing through AC evaporator and diverts it into the vent system or through the heater coil, or any combination in between.  The doors are controlled by a stepper motor. The issue with the system is that the system has to calibrate itself and find the end points of movement before the computer can understand the two closed positions and regulate the temperature.  The photograph shows the blend door actuator motor for the Mountaineer. The fan gear is connected to the blend door and the motor is capable of moving the fan between the constraints of stopping against the motor case. The fan is a 90 degree fan. When it moves between the two stop points, it has 90 degrees of movement capability(180 - 90). The motor is capable of moving the door through a 90 degree arc, but the door hits the extents of movement at 50 degrees. The net effect is that the plastic doors have to absorb the force of the motor driving to a stall point.   The motor is geared to move the doors slowly and with a good amount of force. The door has to withstand the force of stopping the motor, and like bending a coat hanger back and forth, will eventually break. 

Do you have the problem?

The usual symptom is an inability to effectively control the temperature of the HVAC system. The door hangs on a vertical axis, so turning a sharp corner, or fiddling with the fan speed can swing the door into the hot or cold position randomly. While the symptoms are fairly conclusive for blend door failure, the only way to really check it out is to remove the blend door actuator motor and look at the axle.

You can access the actuator motor by fully opening the glove box(squeeze the sides of the box and pull out). The motor is located on top of the heater box behind the glove box door. There are two motor attachment schemes used on Ford. The older models used screws mounting the motor directly to the plenum box. With the screw attachment, you will see two 8mm head screws(note that a 5/16 socket will also work) in the front of the motor. These are easy to remove. There is a third screw that is directly behind the white connector socket that has to be removed with a thin profile ratchet. Remove the three screws and pry up on the motor to remove it. The second attachment method used on later models is a plastic housing that is screwed to the heater box with a plastic pinch attachment that the motor fits on to. The motor is removed by prying up first on the front of the motor and when the front connector releases, pry up on the back connector directly under and behind the white electrical connector. The motor will just pop out.

The picture of two blend doors shows the two most common fail modes. In one the motor connector splits, leaving half of the axle connector. In the other failure, the motor connector breaks completely off. The split failure is shown from the top. Once you have removed the motor, you can check by feel or with a mirror to see if the axle is completely broken off or has half remaining. Either fail mode indicates a broken blend door.

If either of the fail modes is evident, this is a conclusive diagnosis that the blend door needs to be replaced. An alternative that has circulated on the internet is the “nail fix�. This can only be attempted with the split axle fail mode. We had our engineer do an analysis of this repair and the report is posted on our heatertreater.net web site.

Another reported fail symptom is a “clickingâ€� sound coming from behind the glove box. This occurs when the motor gears get out of alignment and are slipping against each other, making the noise. Sometimes you can make it stop by pushing down on the back of the motor and getting the gears to catch.  The failure usually occurs with a broken blend door that allows the motor to get out of alignment and twist slightly, causing the gears to disengage. The HeaterTreater will put the system back in alignment and correct this problem.

The HeaterTreater TM Solution:

This kit replaces the plastic doors and axle with stainless steel components.  All work is done through the glove box opening and no disassembly of the dash or evacuation of the AC system is required.  Tools required are a screw driver, pair of pliers, and a Dremel tool( if you don't already have one, this is a good excuse and the tool has many uses. The area under the dash is confined and you will need either a stubby Dremel tool(~6" long), or a flexible extension for a larger industrial rotary tool. Target has a new rotary cutter product from Durabuilt for ~$30 that includes a flexible extension, variable speed motor, and every grinding bit known to modern Chinese technology(except the one you really need which is included in the HeaterTreater kit ). 

The repair will take about an hour the first time, and once you have experience you can do another car in about 45min.  No extensive mechanical skills are required.  The picture shows the metal replacement kit.  The plastic door is accessed by using the Dremel tool and bit to cut into the plastic heater housing from the bottom.  Complete diagrams for the cutting pattern are provided.  It's a very simple process.  The broken plastic door is removed and replaced with the HeaterTreater TM . 

The instructions are written with multiple pictures and dual level instructions.  You can read the bold print only for experienced mechanics or read the bold and standard for full "instructions for Dummies".  The instructions are almost insultingly simplistic for those who care to read the entire document without admitting that they did it.  The fix is really easy and MUCH preferable to disassembly of the entire dash and engine cooling systems. We provide support via email or phone if required. Our goal is to make sure that every installation is successful. To date we have achieved that goal and have no intention of letting up. This will solve the problems with the blend door and is over-engineered to outlast the Mountaineer.  All our products are designed by degreed professional engineers and manufactured to exacting specifications.  If for any reason the hardware ever fails it will be replaced at no cost. 

100% Made in America

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