c/h wont ignite when switch is turned to either one, i have tried the reset knob and ocasionally it works grateful for any advice as i am without h/w and c/h thanks a lot.
my combi is a valor main combi 24 he.

c t fox, May 2008

it just faults instantly with red warning light but i can hear fan or pump running

c fox, May 2008

ive broke the sequence down into segments which i listed below but that all only takes a second or 2.

can you hear the fan run or anything? or does it just fault instantly?

if i was there i would have front cover off,

when either ch or dhw is demanded i would be looking for the pin to rise and make the microswitch on the divertor assembly. (its the top one not the one facing you) that tells the boiler the pump is running.
ok?, i would be listening for fan starting
then listening for ignition clicking.

and would diagnose from there

iain, May 2008

pessure reading is 2 bar but as soon as i turn knob to water only and turn tap on flame failure light comes on, same aplies to c/h thanks for helping me

c fox, May 2008

whats the pressure reading? in the green? 1 - 1.5 bar

iain, May 2008

basic sequence is,

demand
microswitch (demand acknowledged)
pump runs and proven
fan runs (should hear it)
fan proven
spark ignition (clicking)
burner ignites

where does yours get to?

iain, May 2008