How to diagnose failed auto air vent (AAV) and how to replace expansion vessel on a Vaillant Eco tec boiler step by step
This video is for GAS SAFE ENGINEERS only, always follow manufacturer instructions.
Before to start any work on gas appliance isolate the power, turn off the gas and the waters.
1. Remove front cover
2. Download manual
www.vaillant.co.uk/downloads/...
3. Drain the boiler
4. Leave open the drain point
5. The auto air vent let trough water that is the reason is fault
6. Remove auto air vent bracket
7. Pull out AAV
8. Insert new AAV
9. Close the drain point.
10. Re-pressurise the heating system till 1 - 1.5 bar.