nVent RAYCHEM Raystat-M2 ICE Mode D'emploi page 7

Fault codes
If faults occur, the thermostat disables all outputs and ceases to operate until the fault has been remedied.
TEMP LED flashes red:
Temperature sensor (RayStat-M2-G-Sensor/RayStat-M2-A-Sensor) has been disconnected or short-circuited.
RELAY LED flashes red:
Heating element in sensor (RayStat-M2-G-Sensor/RayStat-M2-R-Sensor) has been short-circuited.
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