Hayward Short Cycling Control or Flow Issue

Heater cycles on and off rapidly (short cycling) without reaching set temperature.

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Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

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Possible Causes

Oversized heater for small body of water, Thermostat sensor placement issue, Flow switch chatter due to variable-speed pump, External control calling intermittently

How to Fix / Troubleshooting

Safety First: Turn off power before adjusting wiring or sensors.

  • Check temperature differential: Ensure the setpoint is at least a few degrees above current water temperature to avoid rapid cycling.
  • Verify sensor location: Confirm the water temperature sensor is properly installed in the header and not influenced by localized hot spots.
  • Stabilize pump speed: Avoid frequent RPM changes while the heater is firing; set a constant speed during heating.
  • Review automation programming: Make sure external controllers are not toggling the heater relay rapidly.
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Repair Difficulty

Medium 3/5

Required Part

Water Temperature Sensor
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