Pressurization Controller

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  • #83645

    Does anyone have experience with rebuilding the Pressurization controller in their 414A or 421C? I have a 414A and my controller seems to be “slow” to respond to significant engine power changes…as well as it pressurizes the cabin 1,000 higher than the dial would indicate. These are not huge problems, but they are annoying.

    I would appreciate hearing about anyone having a controller overhauled. Where did you send it and how much did it cost?
    Thanks,
    Pete

    #95347
    rwelsh
    Participant

      Pete, I have never had any problems with the controller, but I do have the overhaul manual if you want to give it a go. Do you know that the controller uses engine vacuum pump vacuum to open and control the outflow valves and overpressure valve? So if you have a vacuum leak in the lines from the controller to the valves, you will have a slow acting valve. Besides getting the controller out of the panel is a monster job; just stick your head under the panel and take a look.

      Let me know if you want a copy of the manual and an address to send it to.
      Dick Welsh
      dick156@earthlink.net

      #96953

      I too need to have my pressurization controller repaired.

      Does anyone have a shop that can service or overhaul these?

      Dick, do you still have the overhaul manual? I may need to have my mechanic take a look at it…

      My controller at times will get stuck and not rotate itself around to the desired setting. This only happens when the controller is set to the higher altitude settings. It’s like it’s gummed up inside at these higher settings and the motor can’t move the center shaft unless I very litely help it move. Then once it gets a little way down, it resumes on its own….

      Thanks
      Arie

      #96954
      rwelsh
      Participant

        Arie, I have the manuals, but I don’t know if they get into your issue. What motor are you talking about? The outflow vavlves are vacuum operated and as far as I know the controller is manually turned.
        Dick Welsh

        #96957

        Well I wouldn’t say I know exactly how it works.

        But I followed the service manual to test it’s function on the ground. It says to turn on master and pull turn and bank breakers to make the cabin as quiet as possible. Then select a cruise altitude on the controller. You can hear the controller start to turn toward the selected altitude.

        It then says to adjust rate of climb knob and assure you can hear the motor speed up and slow down. Mine does this.

        So the only problem I’m having is when I select a very high cruise/cabin altitude (say cabin 9000ft), the controller stops turning at about 7000ft and won’t move from there, up or down.

        I do have the earlier style pressurization controller, (it’s a grey colored selector knob vs black knob) so I don’t know if this one works different.

        Arie

        #96958
        rwelsh
        Participant

          Arie, there were two different style of controllers. They changed around 1975 to a more modern and user friendly system. It is not easy to get the controller out on my 1977 model. But your does sound like there is a motor that drives something. I will look in the manuals and see if there is any guidance on how to dismantle the controller. It sounds as if something has gotten in the internal gearing. If you could get it apart, it is possible you could correct the blockage. I will look tomorrow at the manuals I have the manuals for both the old and new style.
          Dick Welsh

          #97109

          Hello Pete,

          Yes there is a place in Reno that repairs the controllers. What happens over time is they get gummed up inside and the reference holes and ports become clogged and restricted. The only cure is to repair or replace from Cessna. Last time I checked they were proud to the tune of 5 grand for one. The last one I had repaired was around one thousand. It worked great after and was very responsive, in other words you could adjust the rate of climb and descent like it was designed to do!

          Let me check my records for their contact info and I will repost.

          Peter Danto
          premiere-Aviation Inc.

          #97117

          Peter,
          My plane is in for its annual right now and I am going to have all the static lines checked as well as a few other things recommended by the ops manual. If I am still having problems, I can then be pretty certain the problem is in the controller. I would appreciate the contact information when you get a chance.
          Thanks,
          Pete

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