Boiler Not Heating? A Chicago Troubleshooting Guide
A lot of Chicago's older homes, two-flats, and vintage buildings heat with a boiler and radiators rather than a forced-air furnace. It's a durable, comfortable way to heat — but when a boiler stops delivering heat, the troubleshooting is different from a furnace, and some of it you can safely do yourself.
Here's how to work through a no-heat boiler, from the simple checks to the signs that it's time to call for professional boiler repair before a Chicago cold snap turns it into an emergency.
Start With the Thermostat and Power
Before anything at the boiler, confirm the basics. Make sure the thermostat is set to HEAT and several degrees above room temperature, and replace its batteries if the display is dim or blank. Then check that the boiler's power switch — often a red switch at the top of the basement stairs or near the unit — is on and that the circuit breaker hasn't tripped.
It sounds obvious, but a bumped switch or a dead thermostat battery is behind a real share of no-heat calls. Rule them out before you go further.
Check the Boiler Pressure
Boilers need the right water pressure to circulate heat. Find the pressure gauge on the unit — a cold system should typically read around 12 to 15 psi. If it's reading well below that, low pressure may be preventing the boiler from heating properly, often due to a leak somewhere in the system or a water level that's dropped over time.
Some boilers have a feed valve that can top up the pressure, but if the pressure keeps falling you likely have a leak that needs to be found and fixed. Chronically low or high pressure is a reason to call rather than keep topping it off.
Look at the Pilot Light or Igniter
If the boiler isn't firing at all, the burners aren't lighting. On older boilers that can mean a pilot light that's gone out; on newer ones, a failed igniter or ignition control. Many boilers have instructions printed on the unit for relighting a pilot — follow them exactly, and if it won't stay lit, stop and call. A pilot that keeps going out, or any smell of gas, is a signal to shut the gas off and get professional help rather than keep trying.
Bleed Trapped Air From Radiators
If the boiler is running but some radiators stay cold — especially upstairs — the usual culprit is trapped air. Air pockets block hot water from filling the radiator. On many radiators you can bleed this air out using the small valve at the top: with a radiator key or screwdriver, open it slightly until air hisses out and water starts to dribble, then close it.
If bleeding restores heat, great. If radiators keep going cold or you're bleeding them often, there may be a circulation or pressure problem worth having checked.
When Only Some Rooms Are Cold
Uneven heat — some radiators hot, others cold — points to a distribution problem rather than a dead boiler: trapped air, a stuck zone valve, a failing circulator pump, or balancing issues common in older Chicago systems that have been modified over the decades. These are diagnosable and fixable, but they're a technician's job, not a DIY fix.
When to Call for Boiler Repair
If the thermostat, power, pressure, and ignition checks don't restore heat — or you find low pressure that won't hold, a pilot that won't stay lit, visible leaks, or any smell of gas — it's time to call. Boilers are reliable but their controls, pumps, and safety components need professional service, and a no-heat boiler during a Chicago freeze carries the same frozen-pipe risk as a dead furnace.
Polar Refrigeration & Air Control repairs and installs boilers across Chicagoland, including the older systems common in the city's vintage homes and two-flats. If your heat is out, don't wait for a deep freeze — call (831) 461-3437.
The Polar bottom line
A no-heat boiler often comes down to the thermostat, power, pressure, ignition, or trapped air — and several of those you can safely check yourself. When the simple fixes don't work, or you find failing pressure, ignition trouble, or any gas smell, call a professional before a cold snap raises the stakes. Polar Refrigeration & Air Control services boilers throughout Chicago and the suburbs. Call (831) 461-3437.
Related services & areas
