Thanks for all the info, really appreciate it. After a google and RS Components, I now know what conformal coating and IPA are. I wondered if the chip should pull out but didn't want to try too hard in case I damaged it. By 'deleting the socket' do you mean solder it directly on to the board? Again I'd be worried about damaging the chip from heat as I soldered it or is it not a major problem? Will using IPA and a cotton bud or something like a small toothbrush remove the black gunge?
Good luck with that .... There`s more to the unit than the PCB . Could be a motor fault , gas switch fault , heater fault - some have air flow sensors and other such mysteries .. If you don`t want to spend money just bin it and buy Chinese . The other alternative is send it off to Propex and let them repair / service it , giving you a heater which will give you years of SAFE use - it`s a no brainer .... As said before , Propex provide an excellent service - use them !!
Yep going to send the pcb off to Propex so they can test it and hopefully repair it. The blower's fine on cold so pretty sure it's ok. Thanks for all the input guys.
Not that it really matters but yes you could carefully remove the chip from the socket and solder it into the PCB directly. They only socketed it because they could update the software by making the PCB with just the socket and then plugging in the latest version of the chip. Most components on a PCB can withstand the package getting hot enough to melt solder on the pins. Hand soldering is more likely to damage the PCB than the components. However it is also possible that one of the faults is that the software has been erased by aging .. older flash based chips were only guaranteed for 10 years although many are still soldiering on 20 to 30 years later. And corrosion likely to have nobbled the PCB might also have turned combustion chamber components into rusty colanders.
Oh I’m not liking the sound of that! Still, fingers crossed they can repair the pcb and the rest is ok.