System Description

Electronic Climate Control (ECC) is used on Cadillac Deville and Fleetwood models. FWD models equipped with the HT4100 DFI engine, are equipped with a Body Control Module (BCM) and an Electronic Control Module (ECM) system. The ECM system is used primarily for engine control functions and the BCM is used to control body components (lights, A/C, etc). These systems are linked together through a microprocessor and use the ECC Climate Control Panel (CCP) for diagnostics and testing.

The temperature control system provides automatic regulation of vehicle interior temperature regardless of outside conditions. Temperature and mode of operation are selected by push buttons on control panel. The "COOLER" and "WARMER" mode buttons select temperature, while control modes are selected by one of 6 (7 with rear defroster) buttons across bottom of control panel.

A modulator A/C-heater case encloses the evaporator, heater, blower, and doors in one assembly. The CCOT (Cycling Clutch Orifice Tube) refrigeration system is the same as described for other General Motors vehicles with manual A/C-heater systems.

Electronic controls drive a reversible DC motor, which positions the air-mix door in response to temperature changes and control settings. The sequence of events as the programmer moves from maximum A/C to maximum heat is as follows:

• Possibility of recirculated air is terminated.
• Heater control valve opens.
• Blower speed gradually decreases from Hi to Low.
• Air-mix door starts to move and blends in hot air.
• Mode of air delivery changes from A/C to heater.
• Blower speed increases gradually from Low to Hi.
• Air-mix door reaches "Max Heat" position.

The sequence of events is reversed as the programmer moves from maximum heat to maximum A/C.