3 or 4 weeks ago my trusty 12 year old Prima 80F boiler stopped working. At the time I gave it a (small well calibrated) thump. It started working again and I thought no more of it.
Today it failed again. In the specific failure mode:
...The controls are calling for heat. ...The pump is running and the fan is on. ...The pilot light is lit ...but no main burner.
I took off the bottom cover and can see the gas valve is connected to the electrical control PCB/gubbins by a 4 way MOLEX style connector.
* If I carefully wiggle this connector the main burner lights straight away. * If I turn down the temperature control it turns off the main burner as you would expect. * When I turn up the temperature the boiler *sometimes* returns to the failure mode.
I sense a dodgy connection or a dry joint.
Q. Is this a common failure mode? Is there a specific connector or component that is the most common source of this problem. The benefit of your experience is appreciated!