Bloody boiler......now what!

[Ianock]

Potterton combi 80,recently changed the main PCB board as the old one fried the top left part of the circuit board.All fine for few weeks until it wouldn't start up(lockout out light was on)tried reset but no luck.
Opened her up & noticed water everywhere dried her out with hair dryer & bog paper & she started....ahhh heat & hot water
Few days later same again,now it seems to be coming from the auto air vent down the pipe & splashing over the electrics.This morning(boiler off)there was a loud ticking(relay?)from the front control panel,I switched it off at the mains & found water dripping onto this
My question is,is it easy to change this air valve or could there be a fault elsewhere in the system? I have noticed when you turn the hot water on then off the boiler makes a loud banging noise(once its been turned on/off its ok after that),could this be related?
My second question is why oh why didnt I join one of the heater insurance breakdown plans

 

[kevplumb]

aav is easy enough to change remember to isolate and drain the boiler first tho

 

[Ianock]

Cheers Kev,
A further question,I have just drained the system & started to refill but water is coming out of the aav & falling inside the boiler again,there is a screw on top of the aav but the manual says to leave this loose?

 

[kevplumb]

it should be left loose

if it's leaking replace it

 

[ChrisR]

A "pattern" spare will do as long as it's fairly narrow. Be careful not to turn the pipe it sits on; the nut below is hard to get at.
Nice boilers, combi 80/Pumas.