Carrier HH18HA493 Limit Switch

The Carrier HH18HA493 is a limit switch, a temperature-sensing safety control used in Carrier heating equipment. It opens the control circuit when the temperature at the switch rises above its set point, shutting down the heat source, and resets once the temperature falls back to a safe level.

Repeated limit trips usually indicate an airflow problem such as a dirty filter, a failing blower or restricted ductwork, so check airflow when replacing the switch. This is a genuine Carrier replacement part; confirm the part number on the existing switch before ordering.