E13
Main Communication Fault with External Control or Sensor

Boiler displays E13, particularly when using weather compensation or advanced controls

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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

Open circuit on eBus/communication line, Incorrectly wired room sensor, Faulty weather compensation sensor, Incompatible control connected

How to Fix / Troubleshooting

Safety: Isolate power before working on control wiring. Low-voltage circuits still require care.

  • Check control wiring: Inspect the two-core communication cable between the Main boiler and the external controller or sensor for damage or loose terminals.
  • Temporarily disconnect controls: Remove the external control wiring from the boiler and fit a link across the basic thermostat terminals. If E13 clears, the issue lies with the external device or wiring.
  • Verify compatibility: Ensure that the connected controller or sensor is approved for use with the specific Main boiler model.
  • Engineer checks:
    • Test continuity and polarity of the communication bus.
    • Replace the outdoor sensor or room unit if it fails resistance or communication tests.
    • Check the boiler PCB communication port for damage.
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Repair Difficulty

Medium 3/5

Required Part

Weather Compensation Sensor
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