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Thread: Hayward H350 LO light

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    Hayward H350 LO light

    Hi All,

    Having some issues with my pool heater. Went to fire it up for the first time in a few months last night and all that would happen is as soon it tried to kick on it would light the service light and LO would be on the screen.

    Since I last used it two things have happened:

    1. The pool filter was cleaned.

    2. The keypad on the heater was replaced by me.

    Since #1 & #2 this was the first time we tried to use the heater. The new keypad was a little different looking that what was on there before. Could it be as simple as the incorrect keypad? I live in California, I know Hayward has part numbers with -CAL after them. Not sure if this means california or not. I didnt get a keypad with -CAL after it. I bought this one:

    Could either of these things cause this issue or could it be something totally different and unrelated?
    13,750 gal Fiberglass
    Sta-Rite System 3 Sand Filter
    FC - 8
    pH - 7.7
    TA - 80
    CH - 140
    CYA - 60

  2. Back To Top    #2

    In the Industry
    ps0303's Avatar
    Join Date
    Jul 2011

    Re: Hayward H350 LO light

    Keypads aren't specific to CA so that's not the issue. One possibility is a bad pressure switch, you can locate the pressure switch on the right side of the heater behind the plastic outside black panel, disconnect the wires to it and jumper those two wires together. If the LO goes away and the heater fires, you need a new pressure switch. More than likely this is the issue.

    A word of caution: When working with gas and electrical you might want to consider a licensed contractor. Consider the value of your life and others around you.

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