Elecro Short Cycling / Unstable Control

Heater cycles on and off rapidly, causing temperature to fluctuate and contactor to chatter.

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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

Oversensitive thermostat differential setting, Poor water mixing around temperature sensor, Loose sensor connection causing intermittent readings, Undersized circulation pump causing marginal flow

How to Fix / Troubleshooting

Safety first: Isolate power before adjusting internal settings or wiring.

  • Check sensor placement: Ensure the temperature sensor is in the main flow and not in a dead leg or bypass.
  • Inspect sensor wiring: Tighten any loose connectors and secure the cable to prevent vibration-induced intermittency.
  • Adjust differential (if available): In the installer menu, increase the temperature differential (hysteresis) slightly to reduce rapid cycling.
  • Improve flow: Verify that the pump is correctly sized and that valves are fully open to the heater.

If cycling persists, the thermostat or control PCB may be faulty and require replacement.

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Repair Difficulty

Medium 3/5

Required Part

Elecro Digital Thermostat / Water Temperature Sensor
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