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  1. #1
    Join Date
    Jun 2016
    Location
    Australia
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    Panasonic Piping Thermistor Fault



    Hi Guys,
    I have a Panasonic ducted reverse cycle air conditioner which I believe has a faulty indoor piping thermistor. It keeps turning itself off every 5 minutes and shows a fault code F4.

    I confirmed the fault by disconnecting the thermister on the circuit board and replacing it with a 56K resistor. The A/C appeared to operate ok with a resistor in place of the thermistor, however I'm not sure what the consequences are if I continue to operate it like this. I considered dismantling the Indoor unit to access the thermistor, but after examining the indoor unit, it doesn't appear particular easy to dismantle.

    Could someone advise if operating the A/C without the piping thermistor working (as I described above) will have any undesirable effects. Alternately, does anyone have a service manual showing how to dismantle the unit

    Model: CS-80E90XP



  2. #2
    Join Date
    Aug 2009
    Location
    Dartford
    Age
    34
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    88
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    15

    Re: Panasonic Piping Thermistor Fault

    The sensor will give some feed back to the outdoor to modulate the expansion valve or some sort depends what this thermistor controls. So in the long run yes it would.

  3. #3
    Join Date
    Oct 2001
    Location
    Nottingham UK
    Posts
    5,733
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    51

    Re: Panasonic Piping Thermistor Fault

    Sounds like the sensor is detecting low evaporator temperature and going into frost protection mode.

    I would investigate the refrigerant charge to make sure this is OK before suspecting the sensor

  4. #4
    Join Date
    May 2006
    Location
    Hayling Island, UK
    Age
    60
    Posts
    143
    Rep Power
    21

    Re: Panasonic Piping Thermistor Fault

    The pipe sensor has two main functions
    1. Cooling - Frost protection
    Check: clean filters; clean fan blades, restrictive ductwork; gas charge etc
    2. Heating - Overheat protection and preheat fan control
    Check: same as for cooling above really
    A 56k resistor equates to approx. +2.5°C
    My money would be on poor duct design \ grille selection restricting air flow.
    Cheers
    Loops

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