Potterton Kingfisher Mf 100

[Maxmouse]

Advice please.
The boiler main burner doesn't fire unless the front panel is removed.
With the panel removed the boiler functions completely normally.
All electrical tests as per installation servicing manual are normal.
As soon as the front panel is replaced the main burner extinguishes and the boiler returns to pilot cycle.
Flue appears clear.
Could this be the gas valve, I can't see why it would work with the panel removed if it was.
Any thoughts would be appreciated.
Thanks

 

[Rickster123]

Hi Maxmouse,

Have you had the boiler serviced recently?

 

[Maxmouse]

About 9 months ago.
The system runs on Solar for the summer and this is the first time its really had any work to do since spring.

 

[vectra65]

if fitted with air pressure switch check that