4Y (223) - Flow temperature sensor (CH-NTC) faulty

What does 4Y mean?

This error indicates a problem with the central heating flow temperature sensor (CH-NTC). This sensor is vital for measuring the temperature of water flowing out to your heating system.

• Flow temperature sensor (CH-NTC) is faulty (break or short circuit)
• Corroded or loose electrical connections to the sensor
• Damaged wiring leading to the sensor
• Defective electronic board (PCB)

Click steps to track your progress.

1. 1

   Switch off the boiler. Locate the central heating flow temperature sensor and inspect its connections. Remove the socket and visually check for corrosion or damage.

2. 2

   If you have a multimeter and know the expected resistance values (see NTC tables in a full manual), measure the sensor's resistance. If it's outside the normal range, the sensor may need replacement.

3. 3

   Check the wiring that connects the flow temperature sensor to the main board for any signs of damage, cuts, or short circuits. Repair or replace as necessary.

4. 4

   If the issue persists, and you've confirmed the sensor and wiring are okay, the electronic board (PCB) might be at fault and should be checked by a qualified technician.