F4
Saunier Duval Radio Link Failure to Wireless Receiver

Thermostat shows F4 and cannot detect the wireless receiver or boiler gateway

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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

Wireless receiver (RF gateway) not powered, RF pairing lost between thermostat and receiver, Strong RF interference from other devices, Receiver installed too far from thermostat or behind metal surfaces

How to Fix / Troubleshooting

Safety: Turn off power to the receiver at the fused spur or breaker before moving or rewiring it.

  • Check receiver LEDs: Verify that the Saunier Duval RF receiver or internet gateway has power (status LED on). If not, check the fused spur, plug, or boiler internal connector.
  • Reduce distance: Temporarily move the thermostat closer to the receiver (same room) and see if F4 clears.
  • Remove interference: Keep the receiver away from Wi‑Fi routers, thick metal cabinets, and large appliances. Reposition if necessary.
  • Re-pair devices: Put the receiver into pairing mode (press and hold the link button as per manual) and start pairing from the thermostat menu. Wait until the link LED indicates a successful connection.
  • Power cycle: Turn off the receiver and thermostat for 1 minute, then power back on and test.

If F4 persists with good signal and correct pairing, the RF module in either the thermostat or receiver may be faulty and require replacement.

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Repair Difficulty

Medium 3/5

Required Part

Saunier Duval RF Receiver / Gateway Module
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