A cold house on a Colorado morning is never fun. The good news is that many "no heat" calls trace back to a handful of common problems, and a few of them take only a minute to check. This guide covers the usual suspects, what you can safely look at yourself, and when it is time to call a professional.
Safety first. If you smell gas, hear your carbon monoxide alarm, or see scorch marks near the boiler, leave the home immediately and call 911 or your gas utility from outside. Do not try to fix it yourself.
Three quick checks before anything else
Make sure the thermostat is set to "heat" and the temperature is above the current room temperature. Confirm the boiler has power: check the switch near the unit and the circuit breaker. Then look at the pressure gauge. Most home boilers sit around 12 to 15 psi when cold, but your manual has the exact range for your model.
1. Thermostat problems
Dead batteries, wrong settings, or a faulty thermostat can stop the boiler from getting the signal to fire. Replace the batteries and check the schedule. If the display works but the house stays cold, the control itself may need replacing.
2. Low water pressure
When pressure drops too low, many boilers shut down to protect themselves. Low pressure often points to a small leak somewhere in the system. Topping up the pressure may restore heat for a while, but if it keeps dropping, the leak needs to be found and fixed.
3. Ignition or pilot light failure
On a gas boiler, a dirty igniter, a failed flame sensor, or an interrupted gas supply can prevent the burner from lighting. You may hear repeated clicking with no flame. Gas components should always be handled by a licensed technician. See our gas boiler repair service.
4. Trapped air in the system
Air in the pipes or radiators causes cold spots, gurgling sounds, and uneven heating. The system may need to be bled or purged. If radiators fill with air again soon after, there may be a deeper circulation issue.
5. A failing circulator pump
The circulator pump moves hot water through your home. If the boiler runs and the pipes near it get hot but the radiators or baseboards stay cold, the pump may be weak or stuck. Humming or grinding noises are another warning sign.
6. Stuck zone valves
If only one room or one floor is cold while the rest of the house is fine, a zone valve or its motor may not be opening. This is a common cause of uneven heating and is usually a straightforward repair.
7. Blocked or frozen condensate line
High-efficiency boilers produce condensation that drains through a small pipe. In very cold weather that pipe can freeze or clog, and the boiler will lock out. If you see an error code, check your manual, but do not force the unit to restart repeatedly.
When to call a professional
Call a technician if the boiler keeps shutting off, pressure keeps dropping, you see water around the unit, you hear banging or kettling noises, or the problem involves gas, burners, or electrical components. Repeated resets can make a small fault worse. Our residential boiler repair team diagnoses the whole system, explains your options, and does no work until you approve it.
How to avoid a no-heat call next winter
An annual inspection before the cold season catches worn parts, small leaks, and pressure problems early. Learn more about boiler maintenance. If your boiler is old and breaking down often, it may also be worth comparing repair costs with boiler replacement.