Hayward FDXLTER1931 thermistor for the HDF400 heaterHayward HDF400 Thermistor, FDXLTER1931 In stock$6199
Hayward FDXLTER1931 thermistor for the HDF400 heater
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Hayward HDF400 Thermistor, FDXLTER1931

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$6199
In stock
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Quick overview

  • Genuine Hayward OEM part FDXLTER1931.
  • For the HDF400 listed for the Hayward HDF400 heater.
  • Temperature sensor a thermistor reports water temperature to the heater control.
  • Symptoms of a bad one a drifting or open thermistor shows up as a wrong temperature reading or a sensor fault on the heater.
  • Match the part number Hayward uses several different thermistors across its heater lines, so confirm your heater calls for FDXLTER1931.
  • UPC 0610377406031 the barcode on the genuine part.
Full description and specifications ↓

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Product details

The Hayward FDXLTER1931 is the thermistor, the water temperature sensor, for the Hayward HDF400 gas heater. It is item 10 on the Hayward HDF400 service parts sheet, and it is the Brand OEM part.

What it does

Hayward's H-Series FD manual explains that the thermistor monitors the return water temperature so the heater can hold the selected pool or spa temperature, and it shuts the heater off as the return water reaches 104 F. When it drifts or fails open, the display shows the wrong temperature or the heater reports a sensor fault and refuses to run.

Replacing it

On Hayward H-Series FD heaters the thermistor screws into the inlet side of the header, and its connector plugs into the ignition control board. Hayward's procedure is to turn the pump, gas and power off, drain the heat exchanger, and use new sealant on the thermistor threads when you refit it. Have a qualified technician do the work.

Before you order

Hayward uses more than one thermistor across its heater lines, and FDXLTER1930 is a separate listing for FD heaters. Confirm your heater calls for FDXLTER1931 before ordering.

Specifications
Brand Hayward
Manufacturer part number FDXLTER1931
UPC 0610377406031
Type Thermistor
Fits Hayward HDF400
Shipping weight 0.6 lb
Ships Parcel

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Questions and answers

What people ask about this product, answered by our pool techs.

What heater is this for?
The Hayward HDF400. Confirm the part number FDXLTER1931 against your heater before ordering, since Hayward uses different thermistors on different heater lines.
What does a thermistor do?
It senses water temperature and reports it to the heater control, which uses that reading to decide when to fire and when to shut off.
How do I know mine has failed?
The displayed temperature is wrong or jumps around, or the heater shows a temperature sensor fault and will not run. A thermistor can be checked with a meter for a resistance that changes smoothly with temperature.
Is this a genuine Hayward part?
Yes, it is the OEM Hayward thermistor, part number FDXLTER1931.
Ask your own question