Last weekend our aging boiler went down, showing a few different codes, out with the service manual after some indepth fault finding everything pointed to the main PCB, removed the board to check for dry joints etc on removing the board, I found one of the small PCB jumpers sat in the lower section (these don't just fall off) WTF, looked at the manual to find this jumper should be removed if running on LPG gas!

To my knowledge I'm the only one who has ever had the need to even look in the area the pcb lives in, so worse case scenario it's been like this since install around 16 years ago.

Replacement PCB was £40, it's cost next to nothing over the years, the odd sensor, and heat exchanger clean out, time to look for a one of these new more efficient boilers.