Fault 03 Code 20 — Room temperature sensor faulty, circuit break

What does Fault 03 20 mean?

The Worcester Bosch Greenstar CDi Boiler displays Fault 03 with code 20, indicating a circuit break in the room temperature sensor built into the FW 100 or FR110 controller.

• Damaged or disconnected wiring to the room temperature sensor
• Internal fault within the room temperature sensor itself

Click steps to track your progress.

1. 1

   Inspect the wiring connections to the controller and room temperature sensor for any visible damage.

2. 2

   Ensure the controller is securely mounted and no wires are pinched.

3. 3

   If the wiring appears intact, contact a qualified heating engineer to replace the faulty controller or sensor.