Ford Explorer Nail Fix

This is a description from the HeaterTreater Engineers on the Internet “Nail” fix for the Ford Blend door. The description will describe the fix and outline pros and cons of the fix. HeaterTreater does not accept any liability for the correctness of the enclosed information or the efficacy of the fix.

The Ford Blend Door has two primary failure patterns shown in Fig.1. The door typically fails with either the connector splitting in half or totally breaking off at the top of the door. The Nail fix can only be done if the failure is of the split connector type.

Broken Blend Door

The first step is to remove the actuator motor and check to see if you have a split or broken connector (or no problem at all). There are two motor attachment schemes used on Ford. The older models used screws mounting the motor directly to the plenum box. Access the motor by fully opening the glove box and looking for the motor on top of the heater box in the upper left hand corner of the glove box opening. 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.

Refer to Fig.2 for the next step. Note that the photo is take on a box that has been removed from an Explorer to get a clear view of the axle. You can use a small mirror or just feel the hole in the top of the box where the motor axle extends into the box. Fig.2 shows what the top of the blend door looks like with the split connector fail mode. The “V” shaped remainder of the axle will protrude slightly through the axle hole. If the axle is completely broken, there will be no remnants of the door connector visible.

Top Axle View

If the blend door connection looks like Fig. 2, the nail fix can be attempted. For a completely broken axle, the blend door needs to be replaced.

The motor connector(shown in Fig. 3) is a “dog house door” shaped axle. Looking down at the connector, the right angle of the remaining portion of the connector in Fig. 2 would align with the lower right hand corner of the dog house.

Fan Gear

The end of the axle protruding from the motor will look like this:


The trick is to get a nail through the axle to contact the two edges of the remaining half connector as shown below:


The nail is placed through the axle, contacting the two sides of the remainder of the connector. Rotation is achieved by constraining the broken axle against the heater box opening and turning the motor axle. Note that the nail is shown going through the axle from the lower left to upper right of the dog house.

This forces the lower right corner into the connector as it was originally positioned before the connector broke. The standard fix found on the internet positions the nail as shown below.


Either nail configuration will work. However, the second nail position with the nail protruding through the top of the dog house will not allow the door to move through the full range of normal operation. The motor will hit a stop point on the edge of the motor casing before the door fully closes against the AC evaporator opening. The net effect is that the door will seal off the heater core, allowing efficient AC operation, but will not close against the evaporator opening, allowing ~50% of the air flow to be driven through the heater core and the remainder through the evaporator core. Since the compressor is not running during heater selectiong, this will not cool the air, but will cause a significant loss of heater efficiency.

The nail should be the length of the diameter of the opening of the heater box housing (5/8"), and should be polished on both ends to minimize any scraping or sticking in the housing. The nail should be placed 3/8" from the bottom of the motor axle in order to have it centered vertically in the heater box housing opening.

Our best estimation is that this fix will kinda-sorta-almost-sometimes work. We have no way to conduct long term reliability assessments, so cannot make any statements about the life or potential damage that could be done by the nail fix. One concern is that the axle is not held securely in the center of the blend door connector. This will allow the axle to have some deflection from rotating about a constrained center point. The motor gears are designed to provide rotational force to the axle. If the axle moves out of alignment, this will produce a “twisting” force in the interface between the plastic gears. This could cause stripped gears or a meshing problem that could cause an unconstrained movement of the gears resulting in a “clicking” noise. In our best estimation, the forces generated by the motor during the calibration cycle that caused the original problem of a broken axle will most likely also cause this fix to fail over time. We would consider this to be a temporary fix at best.

We at HeaterTreater have designed a bullet proof fix for the blend door problem that entails replacing the plastic components with metal parts designed to withstand the forces in the system. The repair is done by cutting an opening in the bottom of the heater box, removing the broken door, and replacing it with new hardware. The fix is simple to install and will provide a long term solution that will outlast the vehicle. If you choose to attempt the nail fix, please keep us in mind should the system require further intervention.

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