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Carrier 50HX-48-301 icing up. - Carrier Heating & Cooling

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  • mvpro Dec 21, 2008

    System has the proper ref., both coils cleaned, new filters, good air flows ofm ifm.

    The DB, looks OK and all connections checked.

    The DFT seems stuck open circuit.

    RSV will change and stay in heat mode when DFT is shorted closed.

    My guess is the DFT but I do not know the specs. to test it.

    The RSV may also be intermittently sticking.

    Tired of climbing up on the roof late at night to find the unit iced or stuck in defrost mode.

    I may have another DFT to put on the outdoor coil to rule that out.


  • mvpro Dec 25, 2008

    After cleaning all interconects and relocating the sensor (top of OC), the system is working better than ever.

    No cold air during defrost or icing.

    I will see how it works when the outside temps get lower than 45 F.

    It will keep the entire house above 80 F now.





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That is caused by either................
bad defrost board/sensor
Low refridgerant.
Lack of airflow.

Make sure you have a clean filter and a clean, unobstructed condensor coil.

Refridgerant can legally be cheched only by an EPA certified tech.

You can test the defrost board in a few different ways, but I need more info from you regarding that defrost board before I can go further.

First check the airflow/filter.

Posted on Dec 21, 2008

  • Danny Clark
    Danny Clark Dec 21, 2008

    I would suggest running a test defrost.

    Jump out the sensor (If installed) and the test points to see if it kicks into defrost. By bypassing the other components you can determine if its the board.

    Isn't the timer installed on the board with your unit?

    Defrost boards go bad on a regular basis.

    Judging by your comments on airflow and refridgerant levels I'd say it has to be the D-board and/or timer/sensor.

    Many technicians replace the timer/sensor automatically when a board is replaced.



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