Combustion Safety First.

Illinois winters are merciless. When your furnace fails during a polar vortex, you need a technician who understands combustion physics—not a parts swapper. At Aurora HVAC Services, every heating repair begins with a comprehensive safety audit, including digital combustion analysis to test for the silent, deadly threat of Carbon Monoxide.

Heat Exchanger Integrity.

The heat exchanger is the most critical safety component in your gas furnace. It is a thin-walled metal chamber that separates the combustion gases (including CO) from the breathable air circulated through your home. Every time the furnace fires, the heat exchanger undergoes massive thermal expansion. When the burners shut off, it contracts. After 15-20 years and tens of thousands of thermal expansion cycles, the metal fatigues and hairline cracks develop. These cracks are invisible to the naked eye but allow Carbon Monoxide to leak directly into your ductwork and living space. We use digital combustion analyzers to measure the CO and O2 concentration in the exhaust flue. Elevated CO readings indicate a compromised heat exchanger, and we will shut the system down immediately to protect your family.

Ignition System Diagnostics.

Modern furnaces in the Fox Valley use electronic ignition—either a hot surface igniter (HSI) or a direct spark ignition (DSI) system. HSIs are made of silicon carbide or silicon nitride and are extremely fragile. Over time, they develop micro-fractures from repeated thermal cycling, eventually cracking and failing to glow hot enough to ignite the gas. We test the igniter's resistance (Ohms) and inspect it visually for cracks. We also verify the flame sensor is properly grounded and reading sufficient microamp current (typically 2-6 µA) to signal the control board that a flame is present. A dirty flame sensor is one of the most common causes of intermittent lockouts.

Pressure Switch & Draft Inducer Logic.

Before the gas valve opens, the induced draft motor must create a negative pressure in the combustion chamber, pulling the exhaust gases upward through the flue. The pressure switch verifies this draft exists. If the switch fails to close—due to a cracked hose, a failed motor, or a blocked exhaust vent—the control board will lock out and the furnace will not fire. We systematically test each component in the safety chain: draft inducer motor amperage, pressure switch activation, and exhaust vent obstruction.