how can you tell when the pcb board on a combi boiler is broke?

ok sorry its a vercarra combi, green light is on, no fault indicating lights atr on, and the noilers not attempting to go to ignition at all, but i had the same with a worchester not so long ago but the red fault light was lighting up on that one and it turns out that it was the board gone, so i was just wondering if it could possibly be the board on this one thanks

martyn
June 2009

It's a big question - how can you tell...

Quite a few heating engineers are unable to answer this question - often when thay can't understand a particular fault condition the "go for" the printed circuit board on the off chance that it's defective - very often they'll be right but it doesn't matter if they're not because the customer will pay and the engineer will claim that something else was also defective - "PCB and the Gas Valve govenor - not your lucky day."

In truth, the only way to be sure is to understand what signals/voltages should be present on the various inputs to the board and what corresponding output voltages should be present that match the specific inputs. Some installation manuals that come with the boiler have fault diagnosis charts that provide this information (mine does).

Some boards have a reputation for poor joints and these can sometimes be fixed by examination and resoldering - needs ability to recognise a dry joint. Other PCBs have a history of Electrolytic Capacitors failing - Electrolytes tend to fail if used in a warm environment like inside a boiler.

An excellent article about fixing Potterton Profile PCBs can be seen here...

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

Not a combi so a little less complex I suspect but it gives you an idea - You don't mention your specific boiler make / model what is wrong with it and what you may have eliminated already. Often best when fault finding any system is to go for the easy to test/eliminate and cheap to replace items first.

Good luck...

Peccavi
June 2009