First check the flue outlet is not blocked with a birds nest or similar!
Check that your gas valve is open and gas is getting to the boiler and that you have fuel in your tank or bottles.
Your gas valve (or gas tap) will be in line with the pipe in it´s open position.
Check the gauge on your boiler is at the correct pressure (1.5 – 1.8bar). If the boiler pressure is low top up the heating system. (see point Nº 10)
Do not mistake the temperature gauge for the pressure gauge which reads bar pressure and will measure between 1 and 5.
Check that your radiator valves are all in an open position.
If your radiators are closed down your boiler may overheat and cut off.
Check that your time clock minimum setting is set correctly.
If your time clock is not working, check your batteries are live!
Follow your normal Start up procedure for your heating boiler.
If the boiler fails to fire up straight away, try it again a few times. It may be that your gas needs to be bled up to the boiler. This is especially possible with a long gas run or if you have just changed your gas bottles.
It is common for the circulating pump to jam. If this happens release it with a screwdriver by inserting a screw driver and forcing the pump to turn.
After the system has been running for a while check that your radiators are heating evenly. If you find you have a radiator that isn´t, open the bleed valve with a rad. Key or screwdriver and remove air slowly keeping a bowl handy for water spillage.
After bleeding your system always check your boiler pressure and it top up if necessary if the pressure has dropped. Top the system using the top up valve which you will find situated on the cold water inlet pipe on the boiler.
If you over pressurize your heating system and the gauge rises above three bar pressure, water may leak from the safety valve on your boiler. Don´t Panic! Turn off the tap, as the water leaks out of the boiler the pressure will gradually reduce to working pressure all by itself!
Once you are happy that your system is functioning set your time clock/programmer to auto.