faillure to ignite?

Generally speaking, the servo valve will be sticking (not returning) to allow the diverter valve to shut making both m2 & m3 microswitches. There are various possible causes:

Water section leaking through the stuffing box, causing the pin above to stick up in the sleeve.

Servo valve itself faulty (spring not allowing return).

Blockages in the small tubes to the servo valve (caused by dirt in the system).

Carefree
November 2011