Before you pay for a service call, run through this list. A honest share of “dead furnace” calls end up being one of these — and every one takes under two minutes to check.
1. The Thermostat
Set to HEAT, set above room temperature, and if it uses batteries, swap them. A thermostat with dying batteries can behave in bizarre ways — including doing nothing at all.
2. The Furnace Switch
Most furnaces have a power switch nearby that looks exactly like a light switch. It gets flipped accidentally all the time — by storage boxes, kids, or someone who thought it controlled a light.
3. The Breaker
Check your electrical panel for a tripped breaker. If it trips again immediately after reset, stop — that points to an electrical fault that needs a technician.
4. The Filter
A completely clogged filter can overheat the furnace and trip its safety limit. If you can’t remember the last change, pull it and look. A dirty filter is the cheapest fix in heating.
5. The Gas Supply
Confirm the gas valve on the line to the furnace is open (handle parallel to the pipe). If you smell gas at any point, leave the house and call your gas utility from outside — don’t touch switches.
6. The Condensate Drain (High-Efficiency Units)
90%+ furnaces produce water. A clogged condensate line trips a float switch that shuts everything down. Look for water pooled around the base.
7. The Error Code
Most modern furnaces blink an LED behind a small window on the blower door. Count the flashes and check the legend on the inside of the panel — that code tells a technician exactly where to start.
Still Nothing?
Then it’s time for a diagnosis. Call us and mention what you’ve already checked — it speeds up the repair and sometimes the answer is free over the phone.