Heating & Cooling Problem Helper

How to use this helper

This helper is meant to point you toward the right next step, not to replace an on-site check. Pick the symptom closest to what you are seeing and it will suggest which service page to read and what information to have ready when you call.

Heating and cooling problems often share causes. A clogged filter can make a furnace overheat in winter and freeze an air conditioner coil in summer. A thermostat with weak batteries or bad wiring can look like a failed furnace. Checking the simple things first saves time, but stop at anything that requires opening equipment panels or working near gas or high voltage.

Safe checks before you call

Confirm the thermostat is set to the right mode and a few degrees past the room temperature. Check that the furnace or air handler switch is on and the breaker has not tripped. Look at the air filter; if it is gray and packed, replace it. For a boiler, note the pressure and temperature gauge reading. For an air conditioner, make sure the outdoor unit is not blocked by leaves or debris.

Do not keep resetting a furnace or boiler that shuts down repeatedly. Repeated lockouts usually mean a safety control is doing its job, and the cause needs to be found. If you smell gas, leave the building and call the gas utility or 911 from outside.

When it is time for a technician

Call when the basic checks do not restore heat or cooling, when you hear new banging, squealing or grinding, when water is pooling near the equipment, or when the system runs constantly without reaching the set temperature. Suburban customers can call 847-550-3322; Chicago customers can call 773-250-6060.

Describe the pattern, not a guessed diagnosis

For a furnace, say whether the blower runs, whether the air feels cold and whether the system stops before the room warms. For a boiler, distinguish a whole building without heat from one radiator or zone staying cold. For cooling, describe weak airflow, water near the indoor unit or an outdoor unit that runs while the rooms stay warm. These observations help route the question; they do not identify a failed part.

Include when the problem began, whether it is continuous or intermittent and any message already visible on the equipment display. Read a model label only if it is accessible from a safe, dry position. Do not remove covers, touch hot pipes, open refrigerant lines or adjust gas and safety controls to gather more detail. If a carbon monoxide alarm sounds, leave the building and call 911 from outside rather than waiting for a recommendation.