Boiler not working? Six checks to make before you call anyone
A surprising number of dead boilers are not broken at all. Before you book anyone, these six checks take about fifteen minutes and are all safe to do yourself.
By Dan, Gas Safe registered engineer6 min read
Every autumn the same thing happens. The heating goes on for the first time in months and the boiler does nothing, or runs for a minute and gives up. Some of those calls genuinely need an engineer. A fair few turn out to be a tripped switch, an empty meter or a thermostat with flat batteries. These checks are all safe, none involve opening the boiler, and they are worth doing before you pay for a visit.
If you smell gas, stop here
Do not try any of this if you can smell gas. Call the National Gas Emergency Service on 0800 111 999, turn off the gas at the meter if it is safe to reach, open the windows and get out of the house.
1. Does it have power?
Look at the boiler display. If it is completely blank, check the switched spur next to the boiler is on, then check the fuse box for a tripped switch. If other things on the same circuit are off too, the problem is electrical rather than the boiler.
2. Is gas getting to the house?
Try the gas hob if you have one. If that will not light either, the boiler is not the problem. On a prepayment meter, check there is credit, because the meter can cut the supply when it runs out. If the hob works fine, gas is reaching the house and you can rule that out.
3. What does the pressure gauge say?
Most boilers shut down when the pressure falls too low, often below about one bar. Check the gauge with the heating cold. If it is low, your manual will show how to top it up using the filling loop, usually to around one to one and a half bar. If you find yourself doing this more than once, the pressure is escaping somewhere and that needs finding.
4. Is the thermostat or timer actually asking for heat?
- Turn the room thermostat up a few degrees above the current temperature and listen for the boiler.
- Wireless thermostats run on batteries. A flat battery means the boiler never gets the signal.
- After a power cut, check the programmer clock and that heating is set to on or auto for the current time.
- If you have a smart thermostat, check it is still connected and not in away or holiday mode.
5. Is it freezing outside?
On a cold morning, a boiler that shows a fault and gurgles is very often a frozen condensate pipe, the plastic pipe that drains water from the boiler to outside. Thawing it with warm water, never boiling, and then resetting the boiler usually sorts it. There is a step-by-step guide to that one linked at the bottom of this page.
6. Reset it once, properly
Note down any fault code first, then use the reset button as described in the manual and give it a couple of minutes. If it fires and stays running, keep an eye on it. If it locks out again, stop there. Resetting it over and over does not fix anything and can hide what the fault is.
Signs it needs an engineer
- It locks out again after one reset.
- Water is dripping from the boiler or the pipes underneath it.
- There are loud bangs, whistling or a burning smell.
- You have topped up the pressure and it has dropped again within days.
- It works, but only sometimes, and the problem keeps coming back.
Leave the casing on. Anything inside the boiler is gas work and must be done by a Gas Safe registered engineer. When you call, have the fault code, the pressure reading and the boiler make ready. With those three things I can usually tell you on the phone what is likely to be wrong before I arrive.
Need this doing?
I am Dan, and I cover Preston and the towns around it.