Boiler won't even try to lite? I have an Ideal Classic gas boiler, vented system.Thermo, controls,pump all ok.

I drained the system and replaced a radiator 2 days ago, bled all the radiators and it was working fine. Could it be an air lock in the boiler?Boiler won't even try to lite? I have an Ideal Classic gas boiler, vented system.Thermo, controls,pump all ok.
There are 13 ideal classic boilers in the range, and between 2 and 5 models in each design, but in the main, the overheat stat has tripped, usually on the right hand side of the boiler, if you give exact make and model i will tell you where the reset button is.Boiler won't even try to lite? I have an Ideal Classic gas boiler, vented system.Thermo, controls,pump all ok.
Your boiler would still light even if there was an airlock, but all boilers have an automatic air vent, so there is no air lock in the boiler. You should look to the thermocouple fitting which sits next to the pilot flame. Check that the tip is clean and not worn away, and it is in the pilot flame to get nice and hot. If you don't have a pilot flame , but have electrodes to light the burner, then check that they are sparking. If they are, then your problem is with the gas valve which is failing to open the gas supply to the main burner.
Do as mmpaints said and when it's clean, have a look on thermostat knob next to pilot flame,some time there is a small hole on it which while the pilot flame is on, because on balance between hit ed gas in the tube( thermostat knob is actually a closed ended tube) and the pilot flame, is working perfectly, but as soon as you turn the flame down, ( due to repair or refill of system) that balance will be disturb and it wouldn't work again... if it is so, you have to change the knob, which is like a long (about a meter) of Copper tube, with one end connect to thermostat and the other end sits next to the pilot flame.... very easy to repair.
do you mean the pilot lite wont lite? Have you tried to clean it? It's simple to do, use a safety pin to scrape the junk out or a wire brush designed for cleaning the pilot and a small straw to blow the debris out of it. The additives in the gas tend to build up and give you a lazy flame or no lite at all.