Blend Door Actuator Gear Upgrade Project

[aaron240]

I measured and modeled the existing gear that typically breaks with the hope that i could make a part that was robust enough to outlast the factory piece and limit the amount of time you have to swap out the assemblies. This prototype 3D printed part is made from carbon fiber reinforced nylon 12 and printed using SLS. I will install this in my fiesta ST and provide some feedback as to if it solves the issues we have all experienced with those blend door actuators failing.

 

[Capri to ST]

I measured and modeled the existing gear that typically breaks with the hope that i could make a part that was robust enough to outlast the factory piece and limit the amount of time you have to swap out the assemblies. This prototype 3D printed part is made from carbon fiber reinforced nylon 12 and printed using SLS. I will install this in my fiesta ST and provide some feedback as to if it solves the issues we have all experienced with those blend door actuators failing.

Which of the actuators is that for? I believe there are three, one for the mode, where the air goes, one for the blend, the temperature, and one for fresh or recirculate.

 

[M-Sport fan]

Which of the actuators is that for? I believe there are three, one for the mode, where the air goes, one for the blend, the temperature, and one for fresh or recirculate.

..and I believe that ALL THREE of mine are currently clacking like mad at startup!

 

[thecman02]

Heck yeah. I've had great luck with that material in other applications! Hopefully it works out good for this. On paper its a definite upgrade.

 

[Alkoran]

For those who have access to a 3d printer, the 3D is available since a while. I keep this in my backpocket but never had the chance to test is since I don't have problem with my actuators yet

https://www.thingiverse.com/thing:4512624

 

[ThePorkTree]

Love this conceptually. It's so interesting that everyones last for different lengths of time, which makes me feel like you'd really need to test...20-30 of these and get feedback on the longevity for each.

 

[Intuit]

https://www.fiestastforum.com/threa...-part-numbers-video-install.22458/post-436100

Memory serving, there may be a little potentiometer type system that is supposed to allow the computer to learn then track the blend door's location. I think what happens is that potentiometer wears out or becomes unreliable; causing the HVAC computer to repeatedly grind the gears until they eventually break.

For the driver side one, so far I've had good luck out of the Dorman.
When I though it had failed, it hadn't. I just failed to install it correctly so the drive gear eventually popped-out.
Stuck it back in, installed it correctly this time and been good since.
I suspect Dorman improved the mechanism for tracking the gear's position.

 

[Sam4]

got some no-name from Rock to install this afternoon. 1/4" T15 and gyro spinner, and an upcoming surgeon appt for what remains of my right shoulder....it's got the motocraft-type short part# CYH5E, but is missing the long ford part# from the original. Can't be too many different actual manufacturers of these...

 

[jim.jacoby]

https://www.fiestastforum.com/threa...-part-numbers-video-install.22458/post-436100

Memory serving, there may be a little potentiometer type system that is supposed to allow the computer to learn then track the blend door's location. I think what happens is that potentiometer wears out or becomes unreliable; causing the HVAC computer to repeatedly grind the gears until they eventually break.

For the driver side one, so far I've had good luck out of the Dorman.
When I though it had failed, it hadn't. I just failed to install it correctly so the drive gear eventually popped-out.
Stuck it back in, installed it correctly this time and been good since.
I suspect Dorman improved the mechanism for tracking the gear's position.

I have a hard time rationizing how the feedback sensor could cause these failures. The computer can't "grind" the gears. All it can do is turn the motor off and on. This would have to happen hundreds of thousands of times to induce a fatigue failure. And in gearsets, fatigue failure occurs on the pinion gear, not the bull gear because of the difference in the number of teeth. The bigger output drive gear is the one that always fails. The pinions also fail sometimes due the the trapped debris. So far, I have only had two of the three actuator types fail. The Drivers side and Passenger side (the one behind he glove box). Both look identical from the outside. The keys of the electrical connector are also identical. The one difference is the number of pins in the electrical connector. There are five on the driver side and two on the passenger side. The Driver side actuator has a position sensor on the Output gear (that is what the additional pins are for). I have had teeth break on the output gear on both actuators, so I doubt the feedback sensor is to blame. The teeth just aren't strong enough.
I have two ST's. Between them I have replaced three driver side and two passenger side. The passenger side on the 2016 is starting to clack, now, too. So for my small data set, the probability of failure is the same for both sides (with and without feed back sensor).
I have had similar luck as you with the Dorman replacement. I suspect Dorman is using tougher material for the gears.
Anyway, it seems like the Dorman replacement is better than the Motorcraft.

 

[Intuit]

I have a hard time rationizing how the feedback sensor could cause these failures.

I took it apart; that's how I knew. Actually it's extremely simple.

The system needs to track the location of the blend door. When it can't do so reliably, the motor repeatedly forces the gear beyond it's normal limits for an extended period.

It won't break the gear on the first or second etcetera occurrence of this. It breaks with repeated instances of this. The reliability of the track doesn't fail like an on/off switch but gradually/intermittently/sporadically until it finally just doesn't track any more.

The passenger side behind the glove box only operates when you switch between recirculate and outdoor. Most people seldom operate this side and unlike the other two, I don't hear the system cycling that door with each power on/off of the vehicle; it has a distinct sound. (note: power off cycling is on a ten or fifteen minute delay)

 

[Sprinkle_Star]

I've been doing a long-term experiment after having to replace the mode door actuator twice.

In years prior, I would activate the hvac system by pressing auto, but I've realized if I do that, the blend door actuators are fighting against the air speed from the blower motor.

Nowadays, I turn the hvac system on by setting the fan speed to its lowest setting, allowing the actuators to get into position with the least amount of air resistance, then I click auto about ten seconds afterward.

 

[jim.jacoby]

I took it apart; that's how I knew. Actually it's extremely simple.

The system needs to track the location of the blend door. When it can't do so reliably, the motor repeatedly forces the gear beyond it's normal limits for an extended period.

It won't break the gear on the first or second etcetera occurrence of this. It breaks with repeated instances of this. The reliability of the track doesn't fail like an on/off switch but gradually/intermittently/sporadically until it finally just doesn't track any more.

The passenger side behind the glove box only operates when you switch between recirculate and outdoor. Most people seldom operate this side and unlike the other two, I don't hear the system cycling that door with each power on/off of the vehicle; it has a distinct sound. (note: power off cycling is on a ten or fifteen minute delay)

I have rewritten this reply a couple of times... I think I misunderstood your response when I first read it.
I just took four of them apart to see which teeth are broken. They are all in about the same location on the output gear. That seems to match up with your idea about the position sensor not providing the correct position. Two of the gears that I looked at were from the passenger side, so their failure can't be blamed on a bad position sensor. I suspect the actuator just moves the fresh air door until its fully open or fully closed. but without a feedback sensor, the controller has to guess the position (time, load, who knows?). I rarely cycle this door (as you speculated), so maybe the computer tries to move it to the commanded position each time the car is started since it probably doesn't know where the door is (on startup). Still, the gear is too weak. The gear should be able to sustain the maximum torque that the motor can generate.
Anyway, I now understand the culpability of the position sensor.

 

[Intuit]

I've been doing a long-term experiment after having to replace the mode door actuator twice.

In years prior, I would activate the hvac system by pressing auto, but I've realized if I do that, the blend door actuators are fighting against the air speed from the blower motor.

Nowadays, I turn the hvac system on by setting the fan speed to its lowest setting, allowing the actuators to get into position with the least amount of air resistance, then I click auto about ten seconds afterward.

My prior vehicle had manual blend doors operated by levers on the dash.
It always felt like I could break something if I tried to operate the recirculate door at highway speeds WITH a window open.
May or may not have been the case with the blend door lever; I really don't remember.
So I made it a point to always close the windows before making adjustments.
Reports of anyone needing to fix anything in the forums with that system were nearly non-existent.
So either they weren't breaking or/and people weren't forcing the levers.