1A4 E displayed — Temperature sensor in FW 100 defective

What does 1A4 E mean?

The display on the RT10 or FW 100 control unit shows '1A4 E'. This error indicates that the temperature sensor within the FW 100 unit is not working correctly.

• Defective temperature sensor in the FW 100 unit.

Click steps to track your progress.

1. 1

   Note down the error code '1A4 E' from the display.

2. 2

   Contact a qualified heating engineer or service technician for further diagnosis.

3. 3

   The FW 100 unit or its temperature sensor may need to be replaced by a professional.