No Heating After Summer? Common Boiler Problems When You Switch It Back On
Turned the heating on and nothing happened? These are the faults our engineers see most often on the first cold day in North London — and which you can fix yourself.
You turn the thermostat up for the first time since spring and… nothing. Or a rumble, a fault code and then silence. It is the single most common reason people search for boiler repairs in North London in early autumn, and it is almost always caused by five months of standing still rather than anything catastrophic.
Here's what our engineers find most often on that first cold day in Barnet and across North London.
1. Low system pressure
Check the gauge on the front of the boiler. Below about 1 bar and most modern combis will lock out and refuse to fire. Topping up via the filling loop takes two minutes. If it drops again within days you have a leak somewhere — that needs proper leak detection, not repeated topping up.
2. A seized pump
A pump that has not turned since March can stick. The symptom is a boiler that fires briefly then shuts down on overheat, often with the pipework getting hot right at the boiler but nowhere else. Sometimes a gentle free-off works; often it is a pump replacement, which we carry on the van.
3. Stuck diverter valve — heating cold, hot water fine
If your taps run hot but the radiators stay stone cold, the diverter valve is the prime suspect. It is one of the most frequent boiler repairs we carry out in September and October, and a same-day fix in most cases.
4. Blocked condensate pipe
Debris and summer algae can block the condensate trap, giving a gurgling noise and a lockout code. This one becomes far more common again in December when the external pipe freezes, so clearing it now is worth doing.
5. Airlocks and cold-top radiators
Radiators cold at the top and warm at the bottom just need bleeding. Cold at the bottom and warm at the top means sludge, and that points to power flushing or targeted radiator repairs rather than a boiler fault at all.
6. Thermostat and programmer batteries
Before you call anyone: change the batteries in a wireless room thermostat and check the programmer has not reset to a summer schedule or lost its clock after a power cut. We have driven to plenty of Barnet homes for exactly this.
When to stop and call an engineer
Call us immediately if you smell gas, see yellow rather than blue flames, notice black sooty marks around the casing, or the boiler repeatedly locks out after resetting. Never reset a boiler more than twice — repeated resets can turn a small fault into an expensive one.
Our engineers cover Barnet, Finchley, Whetstone, Muswell Hill, Highgate and Enfield with same-day appointments and fixed-price repairs. If a repair is not economical we'll tell you honestly and quote for a boiler replacement instead.