Call for heat (programmer + thermostat) Fan Runs
Pressure Switch senses fan running and
Pliot light Lights
PCB senses pilot light burning and
Main Gas Valve Opens
The back of the Manual has a fault finding chart.
People say the Printed Circuit Board suffers dry joints and sometimes they're right but not always. You can take the bottom cover off the boiler (one screw under a flap at the bottom) and tap the PCB and other parts with the handle of a wooden spoon to check for bad connections.
If the pilot fails to light suspect the pressure switch. If the pilot does light (it should have a healthy sized flame) suspect the PCB or the main gas valve.
Make sure the over temp stat has not popped - button reset hole on left and underneath of PCB support plate. May have popped because temperature control set too high. Put it on 3 or 4 - not max.
Peccavi, December 2008
