The LEDs under the front panel (the ones that normally indicate preheat temperature - constant = temp, flashing = fault indication) should give you an idea of why the boiler isn't lighting.
Most likely the fault that is stopping the boiler lighting is either the Flue Fan (need the gas man for that one) or an indicated pump fault. I'll assume that it's the latter since you're bleeding the system. These boilers are a real pain to bleed properly as the auto air vent is below the heat exchanger so it's very easy to get air trapped in the heat exchanger, as this is often the highest point in the system. This can lead to an indicated pump fault if an airlock forms and moves round the system to the pump itself, if it spins but is airlocked no water flows and the boiler declares the pump faulty and doesn't light. Check that your automatic air vent is open by taking the big white panel off the front of the boiler (should just lift off) you'll see the pump on the bottom right. On top of the pump, to the rear of the pump casing, you should see the automatic air vent. It has a small black thumb screw on it, turn the little black screw anti clockwise to make sure that the air vent is open.
If you think that there is an airlock here then the best way to try and force the air out is to close (with the boiler off!!) the CH out tap and top the system up from the filling loop. You should hear the air vent hiss as the airlock is forced out. !!Remember to open the CH tap before switching back on!! If you end up over pressurising the system trying to force the air out, remember and let it back down to normal by bleeding water out of a radiator before switching back on.
Of course it may be that the pump and/or air vent are simply faulty!
Jon, September 2006
