Four Seasons 73178 HVAC Mode Door Actuator - Auxiliary

Four Seasons 73178 HVAC Air Door Actuator

The Four Seasons 73178 HVAC mode door actuator restores control of air distribution in the cabin by moving the HVAC air door through its full range of motion. Built as an air door actuator with an arm-style linkage, it is a direct-fit service part for select Cadillac DTS applications with auxiliary climate control.

Key Features

• HVAC mode door actuator for air distribution control
• Arm-style door linkage for the specified application
• 4 mounting ears for secure installation
• 5-terminal pin electrical connection
• Four Seasons Air Door Actuator product line
• Part number 73178 for service matching and lookup

Application Details

Fits 2006-2011 Cadillac DTS, Auxiliary. This Four Seasons 73178 actuator is used in HVAC systems where the mode door must move correctly to direct airflow through the vents, defrost, or floor outlets. It is a practical replacement for a worn or failed auxiliary air door actuator on Cadillac DTS models.

This part cross-references Dayco 73178 for the same application.

What It Helps Fix

• Airflow stuck on one vent setting
• No response when changing HVAC mode selections
• Clicking or binding from a failing actuator
• Incorrect air distribution between dash, floor, and defrost outlets
• Auxiliary climate control door movement problems

Installation Notes

Verify the connector style, terminal pin count, mounting ear layout, and door linkage style before installation. Match the replacement to the vehicle’s auxiliary HVAC position and confirm the original actuator part number 73178 or listed interchange references before service. After installation, cycle the HVAC controls to confirm smooth door movement and proper airflow direction.

Quality Assurance

Four Seasons supplies HVAC service components for repair applications, and this actuator is built to match the specified fitment and electrical/mechanical configuration for the listed Cadillac DTS models.