blend door fix

92-07 Ford F250/350/50 - Heat and AC Blend Door Replacement Parts

  This is a product developed by the HeaterTreater Engineers for the common blend door failure problem on F250+ pickup truck. There was some crossover on the HVAC system used on the F150 and F250-450.  The difference between the two systems is the placement of the HVAC blower motor.  On 150's it is inside the passenger compartment and located under the dash on the passenger side.  On 250+ it is mounted in an assembly on the firewall(see fig 1.) in the engine compartment.  If the HVAC fan motor is inside the cab, check the F150 listing.  If it's mounted in the engine compartment along with a lot of wires and hoses, this is the correct listing.  If there is confusion, you can always send us a picture and we can tell quickly.

 Please check our feedback to get an idea of the product line integrity and customer reaction to our products. We are committed to customer satisfaction and successful repairs of blend door problems. 

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.

                                                   Fig 1.

This is a kit to do a complete repair on the blend door malfunction that is common to F250+.   Every F250 in this range either has, or will have, this common failure over time.  Fig 2 shows the hardware provided for the fix.  All work is done under the passenger side removal of the dash panel or evacuating the AC system and draining the radiator.  Once completed, the alterations are not visible unless you lie on your back in the passenger footwell.  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 two weeks for a full refund(minus shipping).

                                         Fig 2.

The standard fix for the blend door failure is to remove the heater box and replace the plastic door. 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 truck. 1hr work vs 8-14 hours of work, and no specialized mechanical skills required.  The cost of a new plastic door is cheap, but when you include refrigerant, anti-freeze, new AC line connectors, and the time to do the fix, the HeaterTreater is a cost effective and easy solution.


The Problem:

-  The F250 is built with a Blend Door to control the heater and AC function.  On the F250 all air flows through the evaporator core which can be switched on or off to provide cooling.  The air can now flow directly into the vent system or be diverted through the heater core by the blend door.   The door is 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 motor has a larger range of movement than the door will allow. 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. Note that this symptom can also be caused by a bad temperature control knob on the HVAC control panel, and this is a common failure on Ford trucks.  Please check carefully before considering the blend door fix.  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.

Accessing the blend door motor is easy on the F250.

1.      Empty the glove box and fully open it by squeezing the sides in and pulling down.  You will see the plenum box with the acutator on top as shown in fig 1.

2.      The motor is held in place with three squeeze clips.  It's hard to describe, but will be clear when you look at the motor(see fig 3.).  Push the two tabs together while wedging the motor upwards and it will release.  The two front ones are easy to get to, but the one on the back is a little trickier.  If you can't release it by squeezing the tabs, you can always just wedge it out with a large screw driver or pry bar.  

3.      The motor has a long extension that fits into the blend door connector.  You can examine the motor drive shaft for any signs of breakage, but this is not common.  The problem is usually with the plastic connection point on the blend door itself.  On this model, the connection is about an inch below the motor hole and can only be seen by using a mirror.  The easiest way to check the door is to use a 1/4" socket extension.  The square part of the extension will fit into the top of the axle and you can manually turn the door. 

4.       The door should have ~60 degrees of movement between the full heat and full AC position.  Rotate the axle to check the end points and see if the blend door is doing it's job.  You can turn on the HVAC system and check that you can switch between AC and heat manually.  Note that if the movement is greater than 60 degrees, the door is probably cracked and the computer system will detect incorrect end points and not fully close off the evaporator or heater core.

Another reported fail symptom is a "clicking" sound coming from the actuator motor. 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.


                                                 Fig 3.                                                                                                                                Fig 4.

The HeaterTreater TM Solution:

This kit replaces the plastic doors and axle with stainless steel components.  The fix is done by cutting a hole in the bottom of the plenum box in the area shown in Fig 4.  You will need a dremel tool, the cutting bit is provided with the kit.  Once the cut is made, the old plastic door can be removed and replaced with the two piece HeaterTreater door.  The door will insert through the hole in the bottom of the box and the connection axle is inserted from the top where the motor fits.  The motor is then replaced and the bottom cutout piece affixed in place with metal duct tape that is provided with the kit.  You can always use hot glue/epoxy/bondo and sand and paint to make the fix completely invisible if the appearance under the dash is important to you. 

The repair will take about an hour.  No extensive mechanical skills are required.  The picture shows the metal replacement kit.  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 F250/F350/F450.

Patent Pending


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