How to $0.00 cost 98% fix HVAC problem with outside air / recirculate air mode door failure

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My 2013 Raptor overall has been an excellent vehicle with very few problems. Recently though, a very loud hum started from the right side of the dash when I had the heater blower fan on and would get much louder with higher fan speed. This vehicle has the single zone base HVAC system. I assumed that the HVAC blower had bad bearings or maybe something in the squirrel cage causing an imbalance. I removed the blower motor from under the right side of the dash and sure enough found a black cylindrical shaped piece of plastic was stuck in the blower fan cage. I removed the plastic part and put it all back together and the blower fan ran smooth and quiet again. At this point I noticed that there was a constant small purring noise coming from the right side of dash whenever the truck had electrical power on. Doing some research I found that it is a common problem for all F-150s of this cab design generation where the plastic outside air / recirculate air mode door fails at the actuator drive motor end. The cylindrical plastic part in the blower fan was this broken off mode door piece. The purring noise was the inside air / recirculate air mode door actuator motor running all the time. The actuator motor is a simple left / right motor that evidently relies on the mode door closing to home position and loading up the motor to send a signal back to controller to stop. With the mode door broken off of the actuator the motor never sees the close position so just keeps running.

I called a local auto repair shop and the local Ford dealer for estimates to repair and it was extremely expensive requiring basically the whole dash to come out of the vehicle. The inside air / recirculate air mode door and housing unfortunately is located above the HVAC box way up inside the dash. Giving the matter some thought even if I was OK with spending the $2500+ to have the dash removed and the mode door housing assembly replaced, on a 10 year old truck even if the dealer techs were careful there is a pretty good chance that one of the many electrical connectors would be damaged, screws into plastic stripped or cracked, and other things where the mode door might get fixed but there would end up being some other mystery dash rattle, creaking, or intermittent electrical problem. On top of this I rarely use the AC or Heat cab air recirculate function at all. Only on the hottest days of the year when you want Max AC do you ever switch to recirculate air. 98%+ of the time outside air is what you want for cab heat, AC, and windshield defrost / defog. Overall the likely cost and risk of the "surgery" to me outweighed the benefit of having recirculate air function.

No cost solution here is that I took the blower back out and reached up inside and pulled the mode door downward in vehicle position to the outside air position. Gravity down is outside air position for the mode door so this helps. Also with the mode door broken off at the actuator motor end you can sort of jam it and lock it in this position. With the glove box out and the right side dash access panel off you can reach up and feel the mode door actuator motor. Unplug the actuator motor by pulling back on the red plastic connector lock tab first. Disconnecting the power to the actuator motor stops the constant purring noise and does not result in any system fault codes, dash lights, or error messages. This removal and replacement of the blower motor, pulling the mode door to outside air position, and disconnecting the mode door actuator sounds straightforward but given the tight packaging required a couple hours of difficult contortions - but it is possible if you work carefully. With all this done now the truck heat, AC, blower, and distribution to floor, dash vent, and defrost vent functions all work normally and silently. The only thing is that when you push the recirculate air button on the HVAC control the button lights up but nothing really happens.
 

SurfRaptor

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Doorman makes a kit for some vehicles where you cut into the inside of the dash and it allows access to the blend doors and a replacement. They have a template that you trace onto the plastic and I used a Dremel to cut it on an 04 Grand Cherokee.
 
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