Carrier HH18HA493 Limit Switch

Replace your faulty safety sensors with the Carrier HH18HA493 Limit Switch, a precise furnace limit control designed for Carrier, Bryant, and Payne residential heating units. This genuine OEM replacement part is a disc-style, normally closed (NC) safety device that monitors the heat exchanger and inducer housing temperatures. To prevent heat exchanger cracking or component failure, the switch is calibrated to open the circuit at 200°F if overheating occurs and features an auto-reset function that closes once the temperature drops back to 101°F. Engineered for SPST (Single Pole Single Throw) configurations, the HH18HA493 ensures the system remains within safe operating parameters, preventing high-limit trips from escalating into costly repairs.

Key Benefits:

• Exact OEM Specifications: Guarantees proper fit and thermal response times for 58CTA series and related models.
• Automatic Thermal Protection: The 101-200°F auto-reset capability eliminates the need for manual intervention after temporary temperature spikes.
• Critical System Safety: Protects against furnace overheating by interrupting the gas valve circuit when airflow is restricted.
• Klixon Engineering: Built to withstand high-cycling environments found in modern high-efficiency furnaces.

Common Questions:

How do I know if my HH18HA493 limit switch is bad?
If your furnace blower runs constantly but the burners won't ignite—or if the system is short cycling—you should test for continuity across the terminals. A normally closed switch like this should show 0 ohms at room temperature.

Can I use a manual reset switch instead of this auto-reset model?
No. You must always use the HH18HA493 if that is the specified Carrier replacement part for your unit. The auto-reset logic is integrated into the control board's safety sequence.

What causes this limit switch to trip frequently?
Ongoing trips are usually caused by restricted airflow, such as a dirty 1-inch pleated filter, a failing inducer motor, or a blocked secondary heat exchanger.

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.