Boiler Not Producing Heat? Causes and Fixes
The common causes of a boiler that will not produce heat, the safe checks you can do yourself, and when to call a licensed technician.
By the CANRO Heating & Cooling technical team · Licensed HVAC & gas-fitting contractor, Metro Vancouver · Last updated May 2026
A boiler with no heat is often low system pressure, trapped air in the radiators, a failed circulator pump or zone valve, a tripped lockout, or an ignition fault. Checking pressure and bleeding radiators is homeowner-friendly; ignition, pump and gas faults need a licensed technician. Call (604) 359-1081 and we will diagnose it properly.
Why your boiler may not be working
Below are the most common reasons for a boiler that will not produce heat, what each one means, and which you can safely check yourself before calling a technician.
| Likely cause | What it means |
|---|---|
| Low system pressure | Below about 1 bar / 12 psi, many boilers will not fire - often from a leak or a failing expansion tank |
| Trapped air in radiators | Air pockets stop hot water circulating, leaving radiators cold |
| Failed circulator pump | If the pump fails, hot water does not move through the system |
| Stuck zone valve | A failed zone valve leaves its zone cold while others heat |
| Ignition or pilot fault | The burner is not lighting |
| Lockout code | The boiler has shut down on a safety fault and needs diagnosis |
What you can safely check yourself
Before you call, these simple checks are safe for any homeowner and sometimes solve the problem:
- Check the boiler pressure gauge - if it is low, top up per your manual (or call us)
- Look for a lockout light or error code and note it
- Bleed radiators that are cold at the top to release trapped air
- Confirm the thermostat and any programmer are calling for heat
- Make sure the boiler has power and the gas supply is on
- Confirm other gas appliances work
When to call CANRO
If the safe checks above do not restore normal operation, it is time for a licensed technician. We diagnose the real cause of a boiler that will not produce heat, quote a firm price before any repair, and fix it properly - we have served Metro Vancouver since 1999.
Frequently asked questions
Why is my boiler not firing up?+
My radiators are cold but the boiler is on - why?+
Why does my boiler keep losing pressure?+
Do you work on older cast-iron boilers?+
Still stuck with a boiler that will not produce heat?
Get a proper diagnosis and a firm price from a licensed local team. No surprise charges. Serving Metro Vancouver since 1999. Call (604) 359-1081.
