blend door accurator

Discussion in 'DIY Tech Guides' started by datmbn, Feb 15, 2017.

  1. datmbn

    datmbn Junior Member

    31
    2
    This will be a long post about the air control (how I think it works) if there is someone else who knows more, ore if I write somthing wrong,
    so feel free to jump in and correct.


    If there are problems with heat/air flow, chances are it's because one of the accurators sitting on the heater is broken.

    It is 4 x accurators, which 3 are equal and one dissenting.

    It is 1 behind instrument clustr, as I understand regulates the air between the floor and the windshield. Since it sits two servo on the right side of
    heat pack, reachable behind the glove box, the bottom one handles regulation between cold and warm, and the upper regulating air between central air and
    floor / defrost. These three accurators are equally fashiond, and keeps track of where in the regulation they are, using some kind of potentiometer,
    conekted with the rotation.

    then there is a accurator close to the fan motor, which handles switching between fresh air / recirculation, this accurator has no potentiometer,
    so there must be some other way to know when the two positions are reached (do not how).

    The 3 accurators sitting on the heat pack can be exchanged/replaced with each other without problems, just make sure the accurators are
    adjusted to the zero position (arrow mark on the back). it is possible to put one of these also in the fourth place (but not vice versa)

    The symptoms that some accurator is bad, is difficult to regulate air flow or heat, and that you usually hear a popping or grinding
    sound behind the instrument panel when adjusting the heat.

    Fortunately, these accurators are neither particularly expensive or difficult to change, but how do you know which accurators is broken?

    A little rough, I think it is like this:

    1. You can not adjust the hot/cold = lower accurator behind the glovebox
    2. no central air or can not turn off the central air = upper accurator behind the glove box
    3. no heating or no defrost = accurator behind the instrument cluster
    4. no recirculation or no outdoor air = accurators at the fan motor

    When then got off his broken accurator, that's an interesting question what is broken?
    It is quite easy to open the servo, and then see that it consists of an electric motor, via a "transmission" connected to a lever,
    and that there is almost always one gear with teeth broken.

    The question then is why the teeth broke of:
    Bad quality? do not think so when the plastic appears tough and not brittle
    The lever will be hindered in its movement? I can not see any other reason, but it must be such that when the lever is stopped the
    accurator thanks to transmission, is too strong for itself and then broke the weakest gear (which is actually good so that the accurator
    will not be so strong that it breaks the blend doors).

    Why stops the lever?
    It could be due to foreign objects such as leaves, pencils, paper clips, crap, cobwebs, and so forth, gets in the way and stop blend doors.
    A few broken accurators is certainly due to this, but the vast majority probably because the accurator is trying to "go too far" so
    that it stops at the end position.

    As we noted earlier, the car's electronics determine the position in which the servo is using a potentiometer
    coupled to the accurator output shaft. If there is something wrong with this potentiometer, the car's electronics do not know in
    which mode the accurator is, and can then try to run it too far, but I do not think this is the main reason, because if you change
    gear in a broken accurator and re-install it, it tends to continue to work a long time.

    I do not believe that the main cause is physical, but that the "location recognition" will simply be out of synch.

    So here I think that it works:

    When installing a new accurator, there is an instruction that one should pick out the fuse (nr15) belonging to
    heating control, and then turn on the ignition. It is the point that the system will "learn" the values of the accurators and ask them to go to possision 0.
    It would be interesting to do this calibration when you hear the first foult sound from a accurator and see if it helps/accurators will be recalibrated.

    When you then reinsert the fuses and switch on the ignition, the electronics will adjust the accurators until the position that corresponds to the heat/air setting.
    Then, turn a knob to adjust, the accurators goes to the corresponding location, and then when you turn of the ignition all the accurators goes back to 0.
    This is repeated every time you turn on or off the ignition.

    If we think that we have a bad/dead battery causing severe voltage drop at startup, it is not so difficult to imagine that the
    electronics do not think that 0 is 0 longer, but might start counting from 2 instead, and then sufficient movement do not longer exist so the accurator
    stops against its end position.


    It feels a bit like Ford has "failed" to build in some form of fault tolerance.

    You could replace the appropriate gear to a smooth wheel that only transferred power through friction and thus to allow some "slip/self-adjusting"

    I have tried to do just that by replacing the broken gear on a wheel as shown below. This was easily done, just open the servo, remove
    old gear, wash away the grease on friction surfaces, put in the new wheel, and snap together accurator.

    So then you have fixed the accurator and built in a little foult tolerance, for a few kr.
    I have driven on for two months now and it seems to work well.
    I also took the opportunity to clean all channels and blenddoors with compressed air, I even let a little aumont of silicone spray comply with the air flow, so now
    moves all blenddoors almost frictionless. Silicone Spray is almostan invention of the devil, but it is good to lubricate plastic without smudging,
    just be extremely, I mean extremely careful so that it will not spill on any other things.


    Ps. When I bought the gears, I made a wrong order so I got 20 pieces instead of two, so if there is anyone else who wants to try,
    please contact me so I can send you one.

    Sincerely Mats[​IMG]

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    Last edited: Feb 15, 2017
  2. Bnbstang

    Bnbstang Junior Member

    36
    0
    I did all the reseting, and ive sill changed my actuators twice now. I live in az and plastic doesnt last at 120 degrees. If I could find someone with a waterjet id get new gears cut from aluminum. Its just cheap plastic. Not the arm, you can run the with new actuators in and see.