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Thread: hayward H400 natural gas heater

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    hayward H400 natural gas heater

    will not ignite and i get code SF and H5 or HS and the SERVICE light is ON

    What this this mean?


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    In the Industry

    Join Date
    Nov 2010

    Re: hayward H400 natural gas heater

    Likely you have a failed thermister which caused both codes. Replacing the thermister should clear both.
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    Re: hayward H400 natural gas heater

    what does the thermister do?

    thanks for your help

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    Join Date
    May 2007
    South Central NJ

    Re: hayward H400 natural gas heater

    It is a temperature based resistor.

    Here's the Wiki link:

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