baxi combi 80. hot water - ok. ch- nothing

[ianmcd]

as you are not getting any fault code it sounds like the boiler does not have a demand for CH first thing to do is make sure that the selector switch is set to the CH + HW mode and if it is set it to off and come back and tell us what neons are lit with it set to off it could be something as simple as the selector knob shaft has broken , not common with this boiler but not impossible

 

[freezingfergus]

Hi Ian,

The only neon lit at the moment is the 'power on' neon.

The selector is in hw and ch position. When I switch to 'O' the 'power on' neon goes out. Switch to Hw and 'power on' neon comes back on.

Switch back through to hw and ch, 'power on' neon is on but no others.
open a hot water tap and the temperature neons light up in turn and hot water is delivered. Turn off water tap and burner shuts down. Temperature neons extinguish slowly as retained hot water cools.

None of the fault lights have come on at all since this started.

hope this helps.
Tony

 

[ianmcd]

Hi tony it sounds as though the control knob is doing what it is supposed to do, for some reason your boiler is not recognising a call for CH, check all your wiring connections from terminals 1+2 back to the pcb

 

[freezingfergus]

Thanks Ian but I think I've reached the limit of my abilities on this occasion. I've checked connections all through with no joy. I will bring in a professional after the break and explain what's been done.

Once again, thanks for all your help and have a great 2014.

I will keep this thread open and post the result when engineer has had a look.
Bye for now.
Tony

 

[freezingfergus]

Hi all,

engineer came out yesterday pm. I showed these posts and he obviously made his own checks. Suspect PCB.

Arrived this morn and fitted new board. Toastiefergus!

Looking at the underside of pcb revealed a burned out connection from one of the relays.

Thanks again to all.
Tony

 

[JBPHS]

Good do!