SFS red light

My heater has been shutting off when I had the automatic pool cleaner on at the same time. The SFS red light went on in the back of the board. Do I need a new SFS sensor?


  1. Reply

    Darren sometimes the heater could shut off on low flow if you are operating a suction side cleaner ie pool shark and it climbs partially out the pool to the point where the pump loses prime. If you have the SFS light on you would want to first check to see that your Flue temperature is not reaching 500 degrees F when the heater is operating before you replace the Stack Flue Switch. If the Flue temperature is reaching 500 degrees you could also have a bad thermal regulator, bad bypass assy or a sooted/calcified tube sheet. You also would want to check the pins to the PC board for the Stack Flue Sensor are clean and connected. You also would want to make sure your gas water column reading is above the minimum requirement. Make sure your filter and baskets are clean and your psi switch is functioning properly and that you have proper flow.

    If all else fails contact our Service Support Desk to book a diagnostic and repair of your Maxetherm heater.

  2. D Banash


    Does the heater have to get completely delimed and cleaned as part of normal maintenance after a certain amount of years.

  3. Reply

    Darren the Maxetherm heater does not require de-liming or cleaning as a part of normal maintenance. Swimming pool water balanced within the proper parameters as per the Langelier index recommends is usually all the maintenance required. On average a swimming pool heaters natural lifespan is 8-10 years.

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