Furnace Will Not Turn On?
Check These 5 Things First

It is January in Joliet and your furnace is not starting. Check these 5 things before calling a technician — many failures have simple causes.

1. Check the Thermostat

Mode must be set to HEAT. Temperature set above the current room temperature. Fan on AUTO not ON. Batteries not dead. If you have a smart thermostat, check the app for a schedule override.

2. Check the Circuit Breaker and Power Switch

Your furnace uses electricity even if it burns gas. Find the breaker labeled Furnace or HVAC. If tripped, turn fully OFF then back ON. Also check the power switch on the furnace itself — it looks like a light switch and gets accidentally turned off often.

3. Check the Air Filter

A completely clogged filter restricts airflow, the furnace overheats, and the safety switch shuts it down. Hold the filter up to light — if you cannot see through it, replace it. After replacing, wait 30 minutes before restarting so the safety switch can reset.

4. Check the Pilot Light or Ignitor

Older furnaces: look for the pilot flame through the small window. If out, follow the manufacturer instructions to relight. Modern furnaces: you should hear clicking when heat is called for. Clicking with no ignition means a failed ignitor ($150–$300 to replace).

5. Check the Furnace Door and Condensate Drain

Most modern furnaces will not run if the access door is not fully closed and latched. Push it firmly. High-efficiency furnaces: check for water pooling near the base — a clogged condensate drain triggers a safety shutoff.

When to Call Us

Call (815) 212-7662 if: furnace still will not start after checking all 5 items, furnace starts then shuts off after a few minutes, loud banging on startup, furnace runs but blows cold air, or CO detector alarms.

Frequently Asked Questions