Potterton Combi 80 not lighting

[Orchidy]

I have a Potterton Combi 80, which is not lighting, i.e., no flame (or visible spark) when:

(i) the Boiler switched is turned from standby to on and the Central Heating switch is on constant, or

(ii) a hot water tap is turned on

Both the fan and the pump turn on and the water pressure is above the minimum 1 Bar. The red lamp glows when the hot water tap is turned on, and relay 1 appears to be turning on when the Boiler switch is turned from standby to on. The lockout light is off.

The problem started while we were away for the weekend, and as far as I can see we haven't done anything significant that might have affected the boiler.

I have followed the fault finding guide, and the advice of our plumber who managed to have a quick look at the boiler yesterday, and have replaced the Full Sequence Control Board. I did this earlier today (all cables reattached - double checked), but the problem persists!

I'm literally at my wits end, as there is no other diagnosis relevant in the fault finding guide (i.e., it doesn't tell you what to do if the fault persists after replacing the Full Sequence Control Board).

We are a young family and very cold at the moment; on the other hand, our regular plumber is on a 2 week holiday in (warm) Thailand...so any help would be gratefully appreciated.

Thanks in advance and regards to all.

 

[gas4you]

As a general guide if the fan is on but no ignition it would point to the aps not recognising the fan spinning. It could also be a blockage or split in the aps tubes, or in the fan venturi. But then as your plumber replaced the board I assume he checked all of these first

 

[Agile]

Or the gas valve is faulty!

I went to one of these today and although clearly shown as a Combi 80 was an electronic version which I would have expected to be a Combi 80 e.

Tony

 

[Rob]

Only the Puma has a PP version.

 

[Orchidy]

Thanks everyone for your help!

 

[Agile]

And what about your boiler?

 

[baxpoti]

It could also be a blockage or split in the aps tubes,

Check the white APS tube for a split where it connects to the fan box.