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Heater repair - mystery switch

Discussion in 'Troubleshooting and Repair' started by musicboy, Apr 21, 2017.

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  1. musicboy


    Oct 18, 2014
    Hi there,

    Our fan heater gave out, so I opened it up and found the thermal fuse had gone. I ordered another and replaced it, but now when I turn it on something strange happens.

    At first it works fine, then after about 30 seconds there is a spark and it switches off for a minute, before sparking, switching on again and repeating.

    The spark comes from these contacts which are attached to the plate next to the heating element.
    The spark is caused by them separating, but I'm not sure what their purpose is?
    Presumably they separate and close because of the heat causing the metal to contract and expand?
    Are they a safety feature?


    Attached Files:

  2. Minder


    Apr 24, 2015
    Looks like a thermal switch, used to protect overheating.
    I suspect there is not enough air flow and the element is overheating.
    When it opens the element cools and the thermal sw resets itself.
  3. davenn

    davenn Moderator

    Sep 5, 2009

    indeed it is
  4. Alec_t


    Jul 7, 2015
    Try lubricating the bearings of the fan motor.
    Ensure neither the air inlet nor air outlet are obstructed.
  5. elebish


    Aug 16, 2013
    If there is a capacitor in the circuit, check it and replace if needed. Capacitors are sometimes used to keep the arcing at a minimum across contacts! Ed.
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