When the system calls for heat, the boiler sumtimes fails to ignite. If I tap the the bottom of the boiler, the ignition starts and the boiler fires up.

JC, December 2009

Sorry forgot mention that the link to the link to ksijaks is what lead me to the actual capacitor. Very helpful, thank you.

JC, January 2010

I checked this out over the weekend, I found a faulty capacitor, C7 22uF cost 13p to purchase a replacement. Also freshened up all solder joints. Boiler fireing up ok.

Cost of new PCB £150.00 plus plumber fitting charge at about £50.00

JC, January 2010

Actually I agree with you Ste...

I have a lifetime of electronics experience (was never very good) but soldering a few dodgy joints on a bolier pcb is easy for me because of my background - I can imagine though that most people might be frightened of soldering up PCBs and changing components. Boiler PCBs are mostly low tech and many suffer from bad joints - the main problem - as far as I can tell is the failure of electrolytic capacitors - they don't last well in warm environments and the environment in a bolier case tends to be warm...

Good luck...

Mr P, December 2009

id say the same, dry joint faulty relay etc etc but i maybe a well meaning person as mr p states but knowing what can happen if things go wrong, i would not be advising you set about a pcb which controls various settings and safety features with a soldering iron.

good old loop hole again.

why not find a engineer who will charge farely and do the job properly, surely they cant be too hard to find.
after all, i know my pricing is rarely much over the price a member of the public would pay for the part alone due to trade discount and joe public full retail price.

just an opinion.

ste, December 2009

Smells like it might be a bad electrical connection either in the general wiring or on the control board (pcb).

Next time if fails you might consider taking the lower front covers off and gently tapping around with a wooden spoon to narrow down the exact place that needs the bashing.

Here's a link to someone repairing a Potterton pcb - relatively easy for a person confident with a soldering iron.

http://kaijaks.co.uk/blog/nick/2008/02/10/dodgy-old-boiler

Ignore any well meaning person who warns you about the legality of self repair on gas appliances - this link will explain the legal position for a householder...

http://en.wikipedia.org/wiki/Gas_Safety_(Installation_and_Use)_Regulations_1998

i.e. You must be Registered to take payment but just competent if it's your own boiler - competence is not defined in the regulations.

Good luck...

Peccavi, December 2009