The first cold evening comes, you turn the heating on and nothing happens. If your boiler is not working after summer, it’s usually something simple: a timer still on summer settings, low pressure or a part that’s stuck after months of sitting idle. Below are the checks you can safely do yourself in a Bristol home, and the signs it’s time for an engineer. If you’d rather not wait, call us on 01275 400 687 or book a boiler repair.
Why boilers play up after a summer off
Your boiler probably kept heating hot water all summer, but the heating side sat still for months, and parts that don’t move can stick.
The two usual suspects are the pump, which pushes water round your radiators, and the diverter valve in a combi, which switches between hot water and heating. If either has stuck, you might get hot taps but cold radiators, or a boiler that fires up and then shuts down.
Pressure can also drop slowly over the summer without anyone noticing, and sludge settles in the bottom of radiators while nothing is moving.
Quick checks you can do yourself
None of these involve opening the boiler.
- Timer and programmer. Check the heating is switched on and not set to hot water only. If the clocks went back recently, check the time too.
- Thermostat. Turn your room thermostat up a few degrees above the current temperature. A smart thermostat may still be on a summer or holiday schedule.
- Batteries. Wireless thermostats run on batteries, and flat ones often show up in October.
- Gas supply. Check your other gas appliances work and, if you’re on a prepayment meter, that there’s credit.
- Pressure gauge. Most boilers sit at around 1 to 1.5 bar when cold. If it’s well below that, our guide to low boiler pressure explains what to do.
- Radiators. If they’re warm at the bottom and cold at the top, there’s air in them and they need bleeding.
Can I reset my boiler?
If your boiler is showing a fault and has a reset button, you can press it once, following your user manual. If it then runs normally, keep an eye on it.
If it locks out again, don’t keep resetting it. Repeated lockouts point to a fault that needs looking at. Note the code on the display, and if you’ve got a Worcester Bosch, check our list of Worcester Bosch fault codes before you ring, so the engineer has an idea of what to bring.
When to call a Gas Safe engineer
Stop and call an engineer if:
- the boiler keeps locking out after a reset
- you can hear grinding, banging or a loud hum when the heating comes on
- you’ve got hot water but the radiators stay cold
- there’s water dripping from the boiler or pipework underneath
- the pressure keeps dropping after it’s been topped up
These usually mean a stuck pump or diverter valve, a fan or ignition fault, or a leak. They’re engineer-only jobs, so don’t take the casing off.
If you ever smell gas, turn the gas off at the meter if it’s safe to do so, open the windows and call the National Gas Emergency Service on 0800 111 999.
Getting Bristol heating systems going again
Older terraces across the city often have heating systems that have been added to over the years, and sludge is a common reason for cold patches once the heating comes back on.
Bristol’s water is on the hard side, and scale can build up in a combi over time, which doesn’t help a boiler that’s been sitting idle.
How to stop it happening next year
Run your heating for 15 to 20 minutes once a month through the summer. It keeps the pump and valves moving and shows up problems while it’s still warm.
Getting your boiler serviced in late summer helps too. The engineer can spot a sticking part or low pressure before you need the heating, rather than after.
Frequently asked questions
Should I run my heating during the summer?
Yes, briefly. Turning the heating on for 15 to 20 minutes once a month keeps the pump and diverter valve from sticking and helps spot problems early. You don’t need the house warm, so you can turn the radiator valves down if you’d rather not heat the rooms.
Why do I have hot water but no heating?
On a combi, this often points to a stuck diverter valve, which switches the boiler between hot water and heating. It can also be the timer, the thermostat or a pump that has seized. Check your settings first. If they’re right and the radiators stay cold, it needs an engineer.
Is it worth booking a boiler service before winter?
Yes. A service before the cold weather catches small problems before they turn into breakdowns, and it keeps your manufacturer’s guarantee valid. Booking in late summer or early autumn also means the work is done before you’re relying on the heating every day.
Boiler still not working after summer?
If you’ve run through the checks and your boiler still isn’t working, call us on 01275 400 687 or get in touch online. Our Gas Safe registered engineers will find the fault and get your heating back up and running.