Worcester Air Pressure Switch
Part no 87161044610
it will fit to following:-
Worcester 24I Junior FSN NG Combi
Worcester 24I Junior FSP LPG Combi
Worcester 28I Junior FSN NG Combi
Worcester 28I Junior FSP LPG Combi
Worcester 35CDI II FSN NG Combi
Worcester 35CDI II FSP LPG Combi