bolier problem (netaheat profile)

[tiggy]

I need some help with our central heating system, we have a netaheat profile boiler, randall 922 timer control panel & honeywell thermostat ( system aprox 15 years old) it is a pump system & tank in airing cupboard.
The problem is the boiler is makes all the right noises to ignite to heat radiators/water but does not ignite , we have to turn off water & heating on the control panel to get to ignite & then after a couple of cycles will not work again. We have bled radiators for air blockage but not really worked.Any suggestions would be really appreciated.
Thanks

 

[nwlondon]

I have a potterton netaheat profile 50e and the problem I had was fan would come on but not ignite I changed the pcb and air pressure switch and now it works ok. To be honest it was probably the air pressure switch which was faulty but both parts were probably 15 years old!

If you change the air pressure switch (if you still have the originl one which is a white round sealed unit with 3 connectors white orange brown?)the type you get now days is in kit form and its easy to swap out the pcb is a little more difficult but managable

hope this helps

 

[twgas]

can you see a spark through the window, when the fan is running

 

[tiggy]

Can not see a spark when igniting but have had it running on constant & seems to ignit, just when turned back to auto it does not ignite just goes through the cycle of going to ignite.
Really am stumped as do not want to leave heating on all the time.

 

[gasisexpensive]

if 230 volts are on switch live connector during all ignition attempts,firstly i would check flue is not obstructed.
usual parts required for this fault are.pcb,air pressure switch,fan (running slower than required). collapsed flue.
as a diy repair you can exchange the pcb but this boiler needs to be serviced once a year due to safety reasons.
even if pcb is not at fault ,it will be faulty soon as they do break down.so a spare is worth having.