3Y (334) - Differential pressure switch open before ignition

What does 3Y mean?

This fault indicates that the differential pressure switch is open when it should be closed during the boiler's self-check, before ignition. This can prevent the burner from starting.

• Blocked flue gas system or air intake
• Faulty differential pressure switch
• Issue with the fan operation
• Loose or damaged wiring to the pressure switch

Click steps to track your progress.

1. 1

   Turn off the boiler, wait a few minutes, then turn it back on to attempt a reset. Observe if the error code clears.

2. 2

   Ensure that the flue gas system and air intake are free from any obstructions. Check for blockages in the exhaust pipe or air vent.

3. 3

   Inspect the differential pressure switch and its connections for any loose wires or visible damage. If accessible and safe, gently check the hoses to the switch for blockages.

4. 4

   If the problem persists, it may indicate a faulty differential pressure switch or a problem with the fan that requires professional diagnosis.