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Thread: HVAC control swap

  1. #1

    Default HVAC control swap

    Is the analog hvac control from a crown Vic or other marq a plug and play comparable with the “computer controlled” unit?

  2. #2
    2 decades of DDing Box Panthers, now in a Whale VicCrownVic's Avatar
    Join Date
    Nov 2012
    Shelby Township, MI


    The differences will depend on the model year of your car and the model year of the donor car.
    The blend door actuator (BDA) in a manual system might work with the EATC control head. Unless you have an early aero without electronic BDA.
    Manual system does not have a sun load sensor, so you'll add that to make it right. (One or two wires from the sensor in the dash straight to the control head)
    I think the blower motor speed controller for the EATC system is different compared to the blower motor resistor in a manual system. The electrical connector for this may be different between the two and may require adding a wire or a few wires.
    Manual system cars aren't usually equipped with an outside air temp sensor, but might have the wiring there for it so potentially no big deal.

    May need to add input for coolant temp (and maybe VSS signal?). Not sure how you would add either of those inputs. Although when I swapped a '97 EATC control head into The Ice Car ('91 MGM) I didn't provide these inputs to the control head. My '91 had the early EATC control head with slider levers (the reason I swapped, because they were sloppy due to broken sliders), so I didn't have to change the blower motor speed controller. I did change the BDA with the one from the donor '97 car, and I did add the sun load sensor. The rest for a '91 built with EATC was already there, so there was some stuff that I didn't have to do that you will have to do if you want to tackle this swap.
    Last edited by VicCrownVic; 08-03-2020 at 03:30 PM.

    ~ 1998 Mercury Grand Marquis LS - new DD
    ~ 1991 Mercury Grand Marquis LS "The Scab" - plenty of rot, summer DD
    ~ 1997 GMC Yukon - wannabe winter DD - returning summer 2020, I finally have an engine
    ~ 1991 Mercury Grand Marquis GS "The Ice Car" - Rotting Retired Winter DD
    ~ 1989 Mercury Grand Marquis GS - Rotting Retired DD
    Gone but not forgotten:
    ~ 1988 Country Squire ~ 1987 Ford Crown Vic

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