Furnace Not Working? Troubleshooting Guide for Illinois Homeowners

It’s a cold November morning in Illinois, and your furnace won’t start. Before you panic—or pay for an emergency service call—there are several things you can check yourself. Many furnace problems have simple solutions.

Start With the Basics

Check Your Thermostat

It sounds obvious, but thermostat issues cause many “furnace problems.”

Verify these settings:

• Is it set to “Heat” mode?
• Is the temperature set higher than current room temperature?
• Is the fan set to “Auto” rather than “On”?
• Are the batteries fresh (for battery-powered thermostats)?

Try this: Raise the temperature 5 degrees above current room temp and wait a few minutes.

Check the Power

Your furnace needs electricity even if it’s gas-powered.

• Check the furnace switch – There’s usually a switch on or near your furnace that looks like a light switch. Make sure it’s ON.
• Check your circuit breaker – Look for a tripped breaker in your electrical panel.
• Check the outlet – Some furnaces plug into standard outlets.

Check Your Air Filter

A severely clogged filter can cause your furnace to overheat and shut down as a safety measure.

Location: Usually found in the return air duct or blower compartment.

What to do: If the filter is visibly dirty or clogged, replace it and try restarting your furnace.

Gas Furnace Specific Checks

Verify Gas Supply

• Is your gas valve open? The handle should be parallel to the gas line.
• Are other gas appliances working (stove, water heater)?
• Have you paid your gas bill? (It happens!)

Check the Pilot Light (Older Furnaces)

If you have an older furnace with a standing pilot light:

1. Locate the pilot light assembly
2. If it’s out, follow manufacturer instructions to relight
3. If it won’t stay lit, the thermocouple may need replacement

Note: Most modern furnaces have electronic ignition and no pilot light.

Look for Error Codes

Many modern furnaces have LED lights that flash error codes. Check your owner’s manual or look up your furnace model online to decode the pattern.

Common codes:

• Steady light = Normal operation
• Slow flash = Furnace calling for heat but not igniting
• Fast flash = Various errors depending on manufacturer

When to Call a Professional

Some issues require professional expertise and tools. Call an HVAC technician if:

• You smell gas (leave the house first and call from outside)
• The furnace makes loud banging, screeching, or rattling noises
• You see visible damage or rust
• The error code indicates a serious problem
• You’ve tried basic troubleshooting with no success
• You’re not comfortable working around gas or electrical components

Preventive Maintenance Prevents Problems

The best way to avoid furnace breakdowns is regular maintenance. Annual tune-ups catch small problems before they become expensive emergencies.

A professional tune-up includes:

• Thorough cleaning of all components
• Safety inspection
• Efficiency testing
• Filter replacement
• Lubrication of moving parts

Find Help When You Need It

If your troubleshooting efforts don’t solve the problem, don’t wait until your pipes freeze. Find a qualified Illinois HVAC professional who can diagnose and repair your furnace quickly.

Stay warm out there!