Nacelle Tank Flow Switch

Home 2024 Forums Opening Section Maintenance Issues Nacelle Tank Flow Switch

Viewing 15 posts - 1 through 15 (of 16 total)
  • Author
    Posts
  • #83788
    rstanley
    Participant

      Hi All
      Happy Memorial Day !!!
      Does anybody know where I can get a Nacelle Tank Flow Switch rebuilt for a C340A ?
      Thanks for any ideas.
      Cheers
      Richard

      #96083
      rwelsh
      Participant

        Richard, what is the flow switch? Do you mean the switch that turns on the light when the pressure drops?

        #96084
        rstanley
        Participant

          Yes that is it

          #96086

          Have you tried cleaning it out? Does it work electrically? Does it always not work, or just sometimes? Are you sure it does not work? I assume the light works and comes on when tested?

          #96090
          rwelsh
          Participant

            Richard, it is probably a low pressure switch which are sometimes sealed. I would disconnect the two wires from the switch and put an ohmmeter across the two wires. If it is working, you should have continuity as there is no/low pressure on teh switch which should make the connection to turn the light on. I do not have my wiring diagrams nearby so I don’t know it the light on the annunciator panel is turned on with a ground or with power. The light doesn’t work unless the nacelle tank pump switch is on so I would assume the annunicator light need 28 volts to make it light, but it could be the other a\way around. Either way, the low pressure switch should be closed when there is no pressure or low pressure so the continutiy test should tell you if the switch is working or not. If you put some shop air on the switch, then there should be no continuity. If the switch is working correctly, then you have wiring problems or a plug at the switch or before in the pressure line.

            If the switch is bad, the auto ot truck parts store may have one, the only question being what is the PSI the switch should react on. The PSI valve of teh switch may have it stamped on the switch.
            Dick Welsh

            #96103
            rstanley
            Participant

              Dick
              Thanks for your help.
              The REAL problem with this switch is accessibility. You have to remove some “skin” to access it.
              I will try your suggestions when I am ready to “open up the can”.
              Richard

              #96105
              rwelsh
              Participant

                Richard, just where is the pressure switch located? I never looked into where Cessna hid it.
                Dick Welsh

                #96107
                rstanley
                Participant

                  I am not sure but near the nacelle however my mechanic tells me that some “skin” has to be removed.

                  #96110
                  cochrane
                  Participant
                    quote RSTANLEY:

                    I am not sure but near the nacelle however my mechanic tells me that some “skin” has to be removed.

                    For S/N 340A0200 and beyond, you can access this switch through the lower wing inspection panel(s) outboard of the engine. To remove the switch, disconnect the 3/8″ fuel transfer line and nut in the outboard compartment. The switch is then loose in the inner compartment – the other side of the switch is connected to a flexible fuel line. You can probably pull this line and the switch out without removing the transfer pump but the job would be easier if you remove the pump first. I wouldn’t call it readily accessible but you can get to it. To remove and re-install the switch it should be less than 2 hours. If you want a picture of the pump / switch compartment I have one.

                    I provided incorrect information to you on another forum regarding the switch. Cessna used an inexpensive pressure switch (normally closed) on S/N up to ‘200. That switch ‘could’ be replaced with a N.C. pressure switch ( 2 – 7 PSI). However, later S/Ns, and likely yours, moved the transfer pump and pressure switch behind the engine firewall and changed to a flow-through pressure switch – the $2,600 version of a $40 switch. I haven’t found a reasonable replacement but the original was manufactured by Pressure Controls Inc., P/N ON-1.

                    Both versions of the pressure switch are normally closed and supply +28volts to the annunciator panel from the power feed to the pump.

                    #96114
                    rstanley
                    Participant

                      Thanks again for that detailed info.
                      Yes I would like to see a pic of the pump and switch compartment.
                      Thanks
                      Richard

                      #96116
                      cochrane
                      Participant

                        The attached file has the best shots that I have – hope this helps.

                        Geoff


                        Attachments:

                        #96117
                        rstanley
                        Participant

                          Thanks
                          That should help ALOT !!

                          #96123
                          rwelsh
                          Participant

                            Geoff, that was great info and a great picture. Thanks for making the forum such a useful tool.
                            Dick Welsh

                            #96147
                            cochrane
                            Participant

                              I did some research with the manufacturer and found that this switch is manufactured for O&N Aircraft. They apparently re-sell it to Cessna et.al. O&N sells it for $180 (Jim @ O&N 570-945-3769). I assume that O&N has the PMA. That sounds like a reasonable price. The manufacturer said it is slightly different from their standard model ($99).

                              Geoff

                              #96148
                              rstanley
                              Participant

                                Geoff
                                Thanks for the heads up
                                I appreciate your extra effort
                                Regards
                                Richard

                              Viewing 15 posts - 1 through 15 (of 16 total)
                              • You must be logged in to reply to this topic.