Potterton Prima 50F Boiler won't fire up

[AndyN]

I noticed my boiler would keep attempting to start, i.e. the fan would start, but then it would cut out. I checked the operation of the air pressure switch and it seemed to be suspect. I've replaced this but the problem still exists. I've found that if you operate the pressure switch by blowing in the connecting pipes when the boiler is trying to start, you can make it fire up. I have checked all the connecting pipes for blockages or leaks and the little timing choke in the clear pipe is not blocked. If the boiler switches on and off on its own thermostat it can start without a problem. But, if the main room thermostat switches the boiler off, then switches it on again, the boiler keeps cycling with the fan starting and stopping, but he gas never switches on. I have checked the PCB for dry joints and can't see anything obvious, however I'm beginning to think there may be a problem with a sticking relay in the control unit, after I got the boiler to start by tapping the control unit while it was in the 'fan cycling' state. Has anyone got any ideas on what I should try next?

 

[20pictures]

I have a Potterton Suprima 50 that started to to do exactly the same thing last night. Haven't had any luck getting it to relight so would be interested in how you get on.

 

[gstens baxi]

This problem is either the fan or pcb. Call heateam on 08706 096 096 as there call out costs include parts and labour.

 

[andsam]

I have had the pcb fail giving a similar fault. I would check your flue though, I once went to a job that had various parts fit Fan, APS ,etc eventualy found a blockage in the inner flue pipe outside ( a bird ) a long shot but you never know.

 

[jonzeyboy]

Hi,
My boiler decided to stop working today. Pilot light is working although the ignition is still sparking even though the pilot is up. Boiler does not light up on demand from either HW or H. Sounds like the fan is running but not main burner. any help appreciated

 

[jonzeyboy]

I have taken the bottom cover off and pushed the reset button -no difference. I can see a small electric arc on the pcb which is sparking with the ignition-is this normal?