Reznor 209973 Flame Sensor

The Reznor 209973 Flame Sensor is a critical OEM replacement component designed for precise flame rectification in industrial and commercial gas-fired heating units. Engineered for use in the PSE-RZ11 pilot assembly, this sensor monitors the burner flame and transmits a microamp signal to the control board to verify ignition. A fouled or failing HVAC flame rod is a leading cause of intermittent short-cycling and safety lockouts in Reznor unit heaters. By utilizing high-grade ceramic insulation and a temperature-resistant metallic probe, the 209973 ensures stable combustion safety and prevents the dangerous accumulation of unburned gas. This sensor is compatible with a wide range of Reznor equipment, including B 50 and PDH Series models (PDH 100 through PDH 350). When troubleshooting a "no heat" call, replacing a carbon-fouled sensor with this genuine Reznor replacement part restores reliable system performance and maintains strict adherence to factory safety specifications.

• Precise Flame Sensing: Proven DC microamp signal transmission ensures the control board accurately detects flame presence to prevent nuisance shutdowns.
• OEM Compatibility: Specifically engineered as a direct replacement for Reznor 209973 and RZ209973, ensuring an exact fit in PSE-RZ11 assemblies.
• Industrial Durability: Constructed with high-temperature alloys to withstand the harsh environments of gas-fired furnaces and industrial unit heaters.
• Safety Compliance: Functions as a primary safety limit to shut down gas flow immediately if a flame is not established or is lost during the run cycle.

How do I know if my Reznor flame sensor is bad?
If your heater ignites but shuts down after only a few seconds, or if the unit enters a lockout after three failed ignition attempts, the sensor may be fouled with carbon or silica deposits. Measuring the microamp signal with a multimeter is the standard technician's test for confirming a weak signal.

Can I clean the 209973 sensor instead of replacing it?
While cleaning with light steel wool can temporarily restore a signal, it often leaves scratches that accelerate future corrosion. For long-term reliability in commercial applications, a full replacement is the professional standard.

Why does my new flame sensor still cause a lockout?
Ensure the ceramic insulator is not cracked and that the mounting screw is tight. A proper grounding surface is required for the flame rectification circuit to complete; corrosion at the mounting point will prevent the sensor from functioning.

Disclaimer: While we strive for 100% accuracy, product data and specifications are subject to change. Please contact our team to confirm compatibility or technical details before purchasing.