Carrier HH18HA498 Limit Switch

The Carrier HH18HA498 Limit Switch is a high-precision OEM furnace limit control engineered for critical thermal regulation in Carrier, Bryant, and Payne heating systems. This disc-style limit switch functions as a primary safety mechanism, featuring a normally closed circuit that opens on temperature rise to prevent heat exchanger damage or hazardous operating conditions. With a factory-calibrated operating range of 170-210°F, the switch is designed to open at 210°F to halt the ignition sequence and automatically reset at 170°F once the system reaches a safe internal temperature. This automatic reset limit switch ensures continuous equipment uptime for professional HVAC maintenance workflows without requiring manual intervention. Built to exact Original Equipment Manufacturer standards, it serves as a direct drop-in replacement for part numbers L210F-40 and HH18HA498A, maintaining the integrity of the unit’s original safety circuit and providing reliable hi-limit protection for residential and commercial blower assemblies.

• OEM Compatibility: Specifically designed for seamless integration into Carrier, Bryant, and Payne furnace control loops.
• Reliable Thermal Sensing: Provides precise 210-degree open and 170-degree close setpoints for consistent system protection.
• Increased System Safety: Prevents furnace overheating by monitoring air temperature surrounding the heat exchanger and burners.
• Efficient Installation: Features a standard 2.6-inch mounting footprint and simple wiring for rapid field replacement by HVAC technicians.
• Durable Construction: Manufactured with high-grade, corrosion-resistant materials to withstand the thermal cycling inherent in high-efficiency furnaces.

What are the symptoms of a failing HH18HA498 Limit Switch?
A faulty limit switch often results in the indoor blower fan running continuously or the furnace short-cycling (turning off before the thermostat reaches the set temperature). If the switch fails in the open position, the burner will not ignite at all.

How do I verify if this limit switch is tripped or defective?
A technician can use a multimeter to check for continuity across the terminals. Since this is a normally closed switch, it should show continuity at room temperature. If it is open while the furnace is cool, the internal disc is likely damaged and requires replacement.

Why is my furnace tripping this limit switch repeatedly?
Repeated tripping typically indicates an airflow restriction, such as a clogged air filter, blocked return vents, or a failing blower motor, causing internal temperatures to hit the 210°F threshold.

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.