A boiler that refuses to start: a classic winter problem
The thermostat is set correctly, but nothing happens: no noise, no flame, no hot water. This is one of the most frequent breakdowns MLAN Services deals with in Brussels, often at the worst possible moment, in the middle of a cold spell. The good news: the cause is rarely serious, and a few simple checks can sometimes fix the problem before a technician even arrives.
The most common causes of a start-up failure
- Water pressure too low — most boilers refuse to start if the pressure gauge shows less than 1 bar. This is the number one cause of avoidable breakdowns.
- Power outage or tripped circuit breaker — a gas boiler is still an electronic appliance: without power, nothing ignites.
- Gas supply cut off — valve accidentally closed, or meter locked after network maintenance.
- Boiler safety lockout triggered — overheating, a blocked flue, or repeated ignition failure puts the unit into safety mode.
- Faulty sensor or electronic board — on older boilers, a worn electronic component can block the start-up cycle.
- Dirt build-up from lack of maintenance — a dirty burner or scaled heat exchanger disrupts ignition and triggers safety cut-offs.
Checks you can do yourself before calling
- Check the pressure gauge on the boiler (ideally between 1 and 1.5 bar when cold)
- Make sure the room thermostat is switched on, correctly programmed, and its batteries aren't dead
- Check that the boiler's dedicated circuit breaker hasn't tripped at the fuse box
- Check that the gas supply valve is fully open
- Note down the error code or indicator light shown on the boiler's display — it helps the technician diagnose the issue immediately
When should you stop troubleshooting and call a professional?
- A gas smell, even faint: shut off the main gas supply and ventilate before calling
- An error code that persists after a reset
- Unusual noises, smoke or soot marks around the appliance
- A fault that returns after every restart attempt
How much does a call-out for a start-up failure cost in Brussels?
The price depends on the cause identified. MLAN Services always provides a clear on-site diagnosis and communicates the price before any repair, with no surprises on the bill.
Preventing breakdowns: the importance of annual maintenance
Most start-up failures are linked to wear or a lack of regular maintenance. In Belgium, annual maintenance is mandatory for gas boilers. Find out more in our article on boiler maintenance.
Boiler repair in Brussels with MLAN Services
MLAN Services responds quickly for all brands (Vaillant, Bulex, Bosch, Remeha, Daikin) to diagnose and repair a boiler that won't start. Free call-out in Brussels, available 24/7. Call 0491 12 02 33 for an immediate diagnosis.