Lennox 88W59 Pressure Switch

The Lennox 88W59 Pressure Switch is a critical safety component designed for precise combustion air monitoring in high-efficiency furnaces and air handlers. As a Single Pole Single Throw (SPST) switch, it is engineered to actuate at 0.15" W.C. and reset at 0.34" W.C., effectively preventing operation during unsafe draft conditions or venting obstructions. This genuine HVAC OEM part is the direct performance 103094-01 cross-reference for the legacy Lennox 18L89, ensuring a seamless interface with existing 24 VAC control circuits without the need for mounting modifications.

Rated for extreme environmental conditions, this furnace pressure switch maintains reliable switching logic across a temperature range of -40°F to 185°F. For service technicians, the Lennox 88W59 provides the exact electrical contact rating of 0.5 Amp required by Lennox control boards to maintain system certifications. Replacing a failing inducer pressure switch with this factory-specified unit restores the original pressure-sensing accuracy, protecting the heat exchanger from poor combustion and avoiding intermittent ignition lockouts common in aging residential heating systems.

Key Benefits

• Direct Cross-Compatibility: Engineered as the updated functional equivalent for the Lennox 18L89 pressure switch, providing a drop-in replacement.
• Precision Set Points: Factory-calibrated to 0.15 inch water column actuation to ensure the combustion blower is moving sufficient air for safe ignition.
• Broad Operating Range: Robust construction allows for stable operation in unconditioned spaces, handling temperatures from -40F to 185F.
• Enhanced Reliability: Utilizing genuine Lennox parts preserves the equipment's original safety ratings and prevents "nuisance trips" caused by off-brand alternatives.

Common Questions

How do I know if my Lennox 88W59 pressure switch is bad?
Technicians should check for a "Pressure Switch Open" fault code on the furnace control board. Use a manometer to verify the inducer is pulling at least 0.15" W.C. and a multimeter to check for continuity across the terminals once that pressure is reached. If the inducer is running within spec but the circuit remains open, the switch requires replacement.

What is the difference between the 88W59 and the 18L89?
The 88W59 is the current service replacement for the 18L89. While they share the same physical mounting and SPST configuration, the 88W59 is the most recent technical revision manufactured by Lennox for modern service standards.

Can I use this switch in both horizontal and vertical furnace orientations?
Yes, this switch is designed for standard Lennox furnace platforms. However, always ensure the diaphragm is oriented according to the manufacturer’s installation instructions to prevent moisture accumulation in the sampling tubes, which can lead to premature failure.

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.