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Calibrate a new recirculation door actuator

931 Views 4 Replies 1 Participant Last post by  csigona
I just acquired a 2015 Fiesta SE with noisy HVAC actuators, and replaced both the blend door (left side) and the recirculation door (right side) actuators. Although working behind the steering wheel tried my patience and stamina, once the new blend actuator was in, it worked; the recirculation actuator, however, continues to click. The teeth aren't yet broken, but they will break if I don't figure it out. Here's what I know; I hope you've been here before and can set me straight.

The blend actuator connector has 5 conductors: two are for running the motor, the other 3 are for detecting the position of the gear. Such detection is needed since the door is not just open or closed, but is variable, so that the computer can set it, for instance, to 1/8 open because we only need a little heat. Further, since the computer can detect its position, it won't push it past the end of travel, that is, won't try to close it more than fully closed or open it more than fully open, or else the gear teeth will be stressed and break. The replacement works well.

The recirculation actuator, on the other hand, has only 2 conductors. They run the motor but give no indication of the gear's position. This might not be so serious, since the door is either fully closed or fully open. It's never partially open. Nonetheless, wouldn't the computer need to know when the actuator has reached the end of travel? Is there another sensor somewhere, for instance, built into the door, to say that it's closed? And unlike the blend door which has complex gearing and offers a bit of resistance to the little actuator motor, the recirculation door is simple and offers almost no resistance. So how do the teeth break when there's so little load? My guess is that the computer keeps pushing past when the door is closed, but why?

I studied the mechanism and see that the gear only needs to go 1/4 of a turn to completely close the door, however, when I run the actuator not yet mounted, I see the gear turns almost a full turn. That's a lot more than the 1/4 turn needed. I also see that the teeth jump (click) only when the door reaches the end of travel while closing, not when it reaches the end while opening. I then opened up the actuator and repositioned the gear so it matches the position of the closed door, suspecting that the teeth would now jump when the door opens, but NO! Regardless of where I set the gear, the door opens nicely but closes with the clicking noises. So...

a) Are there sensors built into the door, where the one for the closed position failed and the one for the open position works? That would explain why the original actuator broke its teeth, and why the replacement continues to click after closing.

b) Rather than sensors, does the computer somehow learn the position of the gear, and thereafter, by using a stepping motor, know when it's completed 1/4 turn? I tried disconnecting the battery for around 15 minutes, hoping the computer would learn the limits of the recirculation door when I reconnected the battery, but it hasn't helped.

c) Do I have a bad actuator or the wrong actuator? I guess that's possible, but it doesn't explain how the original broke.

Thanks for reading such a long post. Please reply with any ideas or experienced knowledge. I appreciate your help.
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I reviewed the wiring diagram, and see that there are no other sensors, so my guess at this point is that some sort of recalibration is needed, but I don't see anyone talking about recalibration.
More information: I swapped out a good actuator from a 2014 Fiesta into this 2015 Fiesta and it works; no clicking (jumping gear teeth). I then installed the replacement actuator into the 2014 Fiesta and it fails. Lots of clicking when it closes the recirculation door. This proves to me that the replacement actuator is defective. OK, but why; I wanted to know.

Experimenting further, just for my own education, I plugged the connector into the good actuator but left it uninstalled, that is, just dangling, not attached to the door mechanism, so I could examine the rotation of the gear. The good gear turns almost a full turn, just like the bad one. This description can get confusing so I'll lay it out as a table. In all cases, the actuator is not attached to the mechanism.

2014 Fiesta - good actuator - 7/8 turn
2015 Fiesta - good actuator - 7/8 turn
2014 Fiesta - bad actuator - 7/8 turn
2015 Fiesta - bad actuator - 7/8 turn

So the computer always tries to turn the gear 7/8 turn although it only needs 1/4; and although the actuator reaches the end of travel after only 1/4 turn, the computer continues to apply power to the little actuator motor for a certain number of seconds. The door can't close any further, so the gear can't move any further, but the little actuator motor keeps trying, but can't move. As long as the actuator parts are in good shape, it can stand the stress, but with all this pressure on the gears, something has to give, and it eventually does. Over time, the holes where the gear shafts are mounted wallow out, the gear is no longer firmly held in place, and teeth break. The plastic gears also become more brittle with age and therefore more likely to break.

The only step left is to return the defective actuator and get another, preferably from another manufacturer. I bought it from RockAuto, so it will take a few days before I get to install the new-new replacement. Once I get it, I'll post the final results here, and we can close this thread.

Thanks for reading this saga. I sure hope it helps someone.
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New replacement part arrived. I installed it, and it works well. I connected the cable with the actuator not yet mounted to the assembly and, by turning the ignition key so the fan works, I allowed it to turn until the key (the detect where there's no tooth) was positioned forward, then just pushed the actuator on, aligning it with a little wiggle. Before screwing it down, I pushed the recirculation button a few times to make sure the door opens and closes without gear teeth crunching. Screwed it down, worked the recirculation button again, and I'm finished.

I blame the problem on a bad unit from RockAuto, but they made it good by shipping out another new part and not requiring me to send back the broken one.
Unfortunately there's more to add.

The new replacement part (replacement of the replacement) worked for one day and then failed. RockAuto refunded my money, so I thank them for that, but not that there's no way to leave a comment warning folks away from that brand (SKP). I opened up the failed new part to give it a post-mortem examination. Whereas the original Ford part (original failure) has broken gear teeth, the SKP gears are still intact! This means that there's a lot of slop in how the gears are mounted and how they mesh, and rather than break, the gear teeth jump.

I went to the junk yard (U-pull-it), looked for the newest Fiesta, checked that the recirculation actuator is an original Ford part, removed it, and installed it in my car. It works; for how long, we'll have to see. The price turns out to be more than RockAuto's price for the SKP brand.

My advice: Stay away from SKP. Buy Motorcraft. I can't speak for other brands.
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