In message , Vortex
writes
Hi There,

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.

A three way connector - pilot, main and common




* 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.

Either spurious or you have another problem


I sense a dodgy connection or a dry joint.

Q. Is this a common failure mode?

Yes - bad flow soldering, or a cracked wire in the loom connector

Is there a specific connector or component that is the most common
source of this problem.

Use your eyes grasshopper

The benefit of your experience is appreciated!

David








--
geoff