Most Tucson gas furnaces do not run for months. Dust settles, a filter loads up, and the hot-surface igniter that worked last winter is the part that fails on the first call for heat. The longer description of that season is on furnace repair. This page is the narrower question: the furnace will not turn on, or it will not stay on.
If you smell rotten eggs, stop. Leave the house, do not use switches, and call 911 or Southwest Gas. The form on this page is not an emergency line. A carbon monoxide alarm is the same kind of stop: the steps and the official pages are on carbon monoxide safety.
Symptoms and how they’re checked
No price column. A firm number comes after the equipment is seen. We do not publish a Sabino Creek part price here.
| Symptom | Likely cause | How it’s checked |
|---|---|---|
| Nothing at all when the thermostat calls for heat | Thermostat mode, a tripped breaker, an open blower door, or no call reaching the furnace | Heat, not Off or Cool. Setpoint above the room. One breaker reset. The door has to be on for the switch to close. |
| Inducer runs, then silence. No flame. | Hot-surface igniter, pressure switch, or the gas valve not opening | Watch the sequence: inducer, proved draft, then glow. A cracked igniter can look intact until it is tested. |
| Burners light for a few seconds and drop out | Flame sensor not proving flame | The flame is real and the valve closes. Cleaning or replacing the sensor is the usual repair. |
| Heat starts, then the burners shut off while the blower runs | Limit switch from a packed filter or blocked return | Filter and return grilles before anyone condemns the heat exchanger. |
| Burners stay lit and the blower never starts | Blower motor, capacitor, or the board’s fan output | The blower is supposed to wait until the heat exchanger is warm. If it never starts, that wait is over. |
A light dusty smell on that first fire is covered on heater smells burning. Repeated clicking with no flame is a reason to stop resetting and send the form. The seasonal pass, if the furnace still runs and you want it checked first, is the printable checklist and the heating tune-up.
Name, mobile phone, and ZIP are required. Say what you heard. Street address can wait. We follow up the same business day by phone or email.