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  1. #1
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    Toshiba MAR-F104 R407c



    Hi looking for advice on this system sitting on Preheat/Defrost for hours at a time when asking for heating.
    Have changed outdoor Coil TE sensor and gas charge is fine. When i reset system it runs away fine but wont start up in morning by itself!! just sits with Preheat/Defrost Can anyone help please?
    Last edited by Brian_UK; 10-02-2017 at 06:45 PM. Reason: Moved to correct section.



  2. #2
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    Re: Toshiba MAR-F104 R407c

    has it got a bc box?- solonoid coils used to fail on em for fun- think they should be 47 ohm if good

  3. #3
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    Re: Toshiba MAR-F104 R407c

    Yip it has 2 Multi controller boxes on the system but problem seems to effect a the indoors. Could it be both boxes at fault?

  4. #4
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  5. #5
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    Re: Toshiba MAR-F104 R407c

    when it shows pre heat defrost in the morning before you reset it can u feel any heat going to the indoor unit?- no fresh air unit pumpin cold air in causing it to stay in preheat defrost- try adding a setback temp of say 18 deg when unoccupied

  6. #6
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    Re: Toshiba MAR-F104 R407c

    No fresh air supply to units. Just ducted units with open return grille's on ceiling.

  7. #7
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    Re: Toshiba MAR-F104 R407c

    is it a big ceiling void? maybe duct return air from room?- enable rc sensor to control unit instead of ret air

  8. #8
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    Re: Toshiba MAR-F104 R407c

    Tosh called the BS boxes Multi-Controllers and the discharge gas solenoid valve coils (marked as SVD) were very prone to failure.
    Old (bad) coils were 1200 ohms
    Later good ones are 1500 ohms
    Not 47 ohms Mr Monkey :-)
    If the SVD coils are faulty then and open circuit coil means just a coil failure. As short circuit coil is very likely to have taken the PCB as well - look for burnt opto-triacs on the board (beige coloured chips)
    In either type of failure the result is no heating to one (or more) indoor unit, this will show as preheat defrost on a local controller and won't change unless cooling is selected.
    Cheers
    Loops

  9. #9
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    Re: Toshiba MAR-F104 R407c

    It's a random problem that happens once every day or so. Only way to get it heating again is by master reset!!!( Power on and off again) then all indoors heat fine.

  10. #10
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    Re: Toshiba MAR-F104 R407c

    Hmm odd that it only occurs once a day, then after reset is fine. Question - is the outdoor unit running when the customer says there's no heat? If so.... Here's a long shot but check the reversing valve after defrost operation - I'm wondering if the valve isn't mechanically changing back to heat mode after defrost has finished. Reversing valves are energised for heat mode (so during defrost zero volts). Not a common problem with these systems but they are getting on a bit now and could be suffering a bit of wear and tear. Cheers Loops

  11. #11
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    Re: Toshiba MAR-F104 R407c

    delete the timer schedules and run it 24/7- it may be like me - cant be a**ed in the morning but after a few hrs i get going!

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