How To Fix Hayward Pool Heater 5F Code [Solved]

Hayward Pool heater 5F code or SF code mainly indicates the sensor failure of the heater. Temperature sensor or thermistor failure is specified here for the error indication code of SF.

The root reason behind this error includes a faulty sensor wiring connection with the board, a dirty sensor, or a bad control board. Sometimes, the defective temperature sensor is the only culprit.

Anyway, when the error persists, you will surely have to replace the temperature sensor. But before replacing it, you need to find out which reasons are actually causing it and how to replace this issue effectively.

hayward pool heater 5F code

Read through our comprehensive discussion to learn in detail.

How You Can Fix Hayward Pool Heater 5F Code

Here is the comprehensive guide that will explore all the possible reasons and the methods to fix the 5F/SF.

Note: You can also read how to fix Hayward pool heater H5 code.

1. Faulty Wiring Connection on Circuit Board

As you have read above, 5F/SF is an indication of temperature sensor failure. The first reason behind this issue would be a faulty wiring connection on the circuit board. The temperature sensor or thermistor is securely plugged into the board via wiring. 

But if the sensor is not operating, be sure the connected wires may have cuts or damage. In some cases, the wires are not surely connected to the board. So, for the first troubleshooting stage, we will have to check out the wiring condition of the temperature sensor.


  • Before starting, turn off the heater and also switch off the power connection as well.
  • Now, you have to locate the temperature sensor.
  • For that, drain the water from the heater exchanger.
  • Then, disconnect the side access panels.
  • You will see a temperature sensor in a circuit board connected with wires.
  • Check out the wires deeply.
  • If you notice any visible damage over the wires, replace the bad wires.
  • Now, after connecting the wires, ensure a snug connection of those with the board.
  • Now, reassemble the heater and check out if the sensor is working or not.

2. Corroded Temperature Sensor

If the wires are all right and the error persists, there may be a corroded temperature sensor. Because of a dirty sensor, it fails to continue its function properly, leading to sensor failure. Also, a clogged sensor can’t be able to communicate with other essential heating elements. So, while troubleshooting the sensor failure, you must have to concentrate on this fact as well.


  • Power off the temperature sensor.
  • Remove the side panel access and locate the temperature sensor.
  • Unscrew the temperature sensor from the board.
  • If you are noticing corrosion over the sensor body, clean it with a wire brush.
  • Then, rub the sensor body with a cloth dampened in alcohol.
  • Dry the sensor properly.
  • Reassemble the sensor on the board securely.
  • Now check if the sensor is now working or not. 

3. Bad Control Board

If the sensor wire and positioning are quite perfect, the SF error problem may be occurring from the control board. Though the fact is rare, we can’t ignore this when we are resolving the sensor failure error from the heater. Also, most of the time, it seems that the sensor is fine, but the plugging position means the control board is defective. 


  • You can examine the control board.
  • Check out the voltage reading there.
  • If there has no voltage or any other defects, replace the board.
  • Contact Hayward manufacturers for better suggestions.

4. Reset the Pool Heater

In most cases, a reset will prove well in the case of the heater malfunctioning. Somehow, there are stuck bugs or glitches on the heating elements like sensors. Those create obstructions in operating the heater well.

Anyway, if there are any error codes on the heater, it will automatically do a reset on the heater and assist in resuming the operation. But most of the time, this doesn’t happen, and you will need to reset the heater manually.

Here are the needed steps to do a reset on your Hayward pool heater:

How to Reset the Hayward Pool Heater?

  • To reset the heater, you will have to use the “Mode” button. 
  • Now cycle the button and put the heart in “Standby” mode.
  • After some while, back the heater to the original operating mode like “Pool” or “SPA.”
  • Your heater function is being reset.

5. Damaged Temperature Sensor

Finally, if all the above steps have been ruled out, a damaged temperature sensor or thermistor is the only reason for persisting SF error. The sensor can be damaged for using it for longer times. Sometimes, faulty handling of the heater also leads to this element failure. 

Anyway, without any late, you will have to replace the sensor to back the heater to operate again. Follow the below instructions to replace the bad temperature sensor from your heater:


  • First, turn off the heater.
  • Also, switch off the pump and main gas valve.
  • Disconnect the heater from the electrical connection.
  • Now, disconnect the side panel access.
  • Locate the thermistor from there.
  • Carefully detach the sensor wires from the control board.
  • Unscrew the thermistor and take it out.
  • Replace the bad and old thermistor with the new one.
  • Re-attach the sensor by reversing the above procedures.


How long do Hayward pool heaters last?

The fact depends on the maintenance of the heater. If you properly maintain the heater, it will last long. But from the manufacturer manual, it will last up to 7-10 years on average. 

Will my Hayward Pool heater get clogged?

Yes, the pool heater can be clogged due to improper use of this. For clogged filters and pumps, the heater catches water flow restriction issues. The heater gets overheated, which affects the heater’s normal operation. 

Can chlorine damage the pool heater?

Chlorine can damage the pool heater and its essential elements in several ways. Having a high amount of chlorine will dissolve the pool pump and heater and create malfunctions in valves. Also, it will do internal damage to the heater.

Wrapping Thoughts:

Now you know the actual reason for appearing SF/5F code on the Hayward pool heater. Also, you have learned how to fix this error code more quickly. 

Hopefully, you will easily fix this error code by yourself immediately. But if you are troubled to understand any of the above facts, just leave a comment below. We’ll reply to you ASAP.

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2 thoughts on “How To Fix Hayward Pool Heater 5F Code [Solved]”

  1. 12/23/2022 Memphis, TN
    New pool, 2 1/2 months old. All Hayward equipment including heater. It’s currently 4 degrees here, heater display says F5. Manual says temperature sensor is broken. Company that put in our pool gave us scant information re: operation of the equipment. Your technical support people provide basically no help.
    The manual ,I guess, was written by someone whose native language is not English. Put me down as not a big fan.

    • Hi Joe

      You have already known that the Hayward pool heater F5 error code indicates the temperature sensor failure of the heater.

      However, the root reason behind this error includes a faulty sensor wiring connection with the board, a dirty sensor, or a bad control board.

      Sometimes, the defective temperature sensor is the only culprit.

      Anyway, to fix the er F5 issue, you have to replace the temperature sensor.

      But as your pool heater is a new one & it must cover the warranty period.

      So, before replacing the sensor or doing any checking, it would be wise to contact the Hayward customer support center.

      Hopefully, your heater issue will be solved.

      Wish you all the best!


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