Plumbing Problems in the UK? Ask a Plumber Now.
Hi all boiler are different unfortunately so if you can tell us what make and model it is that would really helpful.
as a general diagnosis. if its a gas boiler i would first look at the pressure switch sometimes the tubes can get blocked.
if its an oil boiler then check you have oil and that the remote acting fire valve (if you have one) has not tripped.
Yes take the front of you see the tubes connected to the switch pull them off and blow through then try gently blowing them when they are connected and see if the boiler attempts to fire. if it does either the fan is not running correctly or your boiler casing is leaking.
If it doesn't, check for a voltage at and across the switch when you blow down the tube. If you have voltage at the switch but not across then its the switch.
If you do not have voltage at the switch check the pcb for a loose connection or burn marks.
A 3 port valve is always open to hot water, if everything is running and the pipe from the boiler is getting hot, check the circulation pump