with demand for heat the fan runs and and boiler begins to spark but will not go to full flame, i have changed fan and aps to no avail.. all hoses are clear and the flue is free from any blockages, any ideas

newtorepair, May 2011

checked inlet pressure and was reading well over 22mb,
cleaned out burner and injector
stripped out gas valve and checked lint arrester (clean as a whistle)
cleaned out pilot assembly..
with only the first three neons lit i checked voltage to the gas valve on the harness and got a constant supply ruling out the pcb...
after speaking to the tech line we came to the conclusion it could only be the gas valve at fault.which is now not even supplying a sufficient pilot

newtorepair, June 2011

thankyou for your advice
im back on the job tomorrow so i will let you know the outcome once i have cleaned the injectors and lint arrester
i have had a few dodgy meter regulators myself so i suppose i should have checked that first.

newtorepair, May 2011

boiler should still fire even with combustion casing off
seals are there to stop products of combustion leaking into room
''room sealed appliance''
it sounds like either
main injector blocked or
debris in gas pipe blocking main injector
check inlet gas pipe to gas valve for blockages
gas valve has a lint arrestor inside
these can get clogged as well
what gas pressures were you getting on inlet?
if all blockages cleared & boiler still fails to light
check dynamic pressure on gas meter
ive known gas meter regulators to fail to maintain adequate dynamic pressure to gas carcass
keep me updated on your progress

manwithnoname, May 2011

yes the pilot does remain lit and the pcb sends voltage to the gas valve... it does do a quick flare up every so often but quickly goes back out.... i will check main burner for any blockages as its not been serviced for several years... would a slight break in the case seals cause this sort of problem?

newtorepair, May 2011

if your capable of changing the fan & APS then you should be OK to do following
im assuming the pilot lights & remains lit
[neons 1, 2 & 3 are lit]
check inlet gas pressure to see if it drops during demand
if it doesnt drop check voltages to gas valve
no voltage to gas valve - check connector on pcb
if voltage on pcb but not on gas valve - faulty harness
no voltage on pcb- faulty pcb
voltage on gas valve - check main burner injector for blockages
ive seen quite a few main burner injectors blocked up
id always do the above electrical checks BEFORE diving into the main burner injector, just to be on the safe side

manwithnoname, May 2011