Hi folks!
Just to let you know, I am not a heating/plumbing engineer, merely your average Joe with a boiler problem. However, I have been an IT engineer for nearly 20 years and I'm very handy on the electronics side of things (have a decent multimeter and good at diagnosing electronic faults and soldering).
Now with that out of the way, I'll explain the fault:
Ok, I have the above model boiler and about 3 weeks ago, it started behaving 'strangely'. First, the red light would keep coming on and I would lose all hot water (CH or DHW). After resetting it each time, the boiler would work ok again.. for a bit.
Eventually, it got worse and then one day, I could hear what sounded suspiciously like electronic relays actually buzzing behind the panel (am familiar with this sound) and the top green light flickering (for the hot water only) at the same time. As this happened, the boiler would get hot then cold then overheat and then OH cut-out would kick in.
So, I opened up the boiler and checked the pcb and discovered a black area. So I completely removed the pcb and discovered that the board was totally black due to over-heating of a zener diode and surrounding resistors - and underneath, major dry solder joints as a result of this.
So I immediately (and foolishly, as you'll find out in a minute) jumped to the conclusion that this was causing the problems. So I ordered a brand new pcb kit (new Honeywell pcb and thermistor) from ebay for only 89 quid, which I thought was a bargain!
You guessed it.. fitted the new pcb only to discover that the boiler is playing up exactly the same as before!! Relays buzzing and not switching properly between CH and DWH modes. So the old pcb, while on it's last legs, was probably just about working ok.. although at a guess would have totally failed inside 6 months, either due to those components overheating and failing or the solder joints becoming completely dry/open circuit.
So, decided to have a bit more of a gander and discovered a hell of a lot of corrosion on the DHW micro switch. After reading quite a few threads on this very forum, it appears that the diaphragm is prone to failure on these and needs to be replaced every 3 years.
It very much looks like that is what has failed and has leaked water all over the switch and corroded it pretty badly to be honest; like a kinda crystalline white material that goes right up the switch body (but not to the spade connectors). Would this cause the weird symptoms I described id this part had failed? And can it be replaced easily?
Many thanks,
Paul.
Just to let you know, I am not a heating/plumbing engineer, merely your average Joe with a boiler problem. However, I have been an IT engineer for nearly 20 years and I'm very handy on the electronics side of things (have a decent multimeter and good at diagnosing electronic faults and soldering).
Now with that out of the way, I'll explain the fault:
Ok, I have the above model boiler and about 3 weeks ago, it started behaving 'strangely'. First, the red light would keep coming on and I would lose all hot water (CH or DHW). After resetting it each time, the boiler would work ok again.. for a bit.
Eventually, it got worse and then one day, I could hear what sounded suspiciously like electronic relays actually buzzing behind the panel (am familiar with this sound) and the top green light flickering (for the hot water only) at the same time. As this happened, the boiler would get hot then cold then overheat and then OH cut-out would kick in.
So, I opened up the boiler and checked the pcb and discovered a black area. So I completely removed the pcb and discovered that the board was totally black due to over-heating of a zener diode and surrounding resistors - and underneath, major dry solder joints as a result of this.
So I immediately (and foolishly, as you'll find out in a minute) jumped to the conclusion that this was causing the problems. So I ordered a brand new pcb kit (new Honeywell pcb and thermistor) from ebay for only 89 quid, which I thought was a bargain!
You guessed it.. fitted the new pcb only to discover that the boiler is playing up exactly the same as before!! Relays buzzing and not switching properly between CH and DWH modes. So the old pcb, while on it's last legs, was probably just about working ok.. although at a guess would have totally failed inside 6 months, either due to those components overheating and failing or the solder joints becoming completely dry/open circuit.
So, decided to have a bit more of a gander and discovered a hell of a lot of corrosion on the DHW micro switch. After reading quite a few threads on this very forum, it appears that the diaphragm is prone to failure on these and needs to be replaced every 3 years.
It very much looks like that is what has failed and has leaked water all over the switch and corroded it pretty badly to be honest; like a kinda crystalline white material that goes right up the switch body (but not to the spade connectors). Would this cause the weird symptoms I described id this part had failed? And can it be replaced easily?
Many thanks,
Paul.
