Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Section 32 (HVAC Systems - Manual): Description
The Heater, Ventilation and Air Conditioning (HVAC) system is a Cycling Clutch Orifice Tube (CCOT) type system, designed to cycle compressor on and off to maintain selected temperature, and prevent evaporator icing. Compressor clutch operation is controlled by the Powertrain Control Module (PCM) by providing a ground path to A/C compressor clutch relay. A/C system is protected by 2 pressure switches. A/C high pressure switch interrupts A/C request signal when line pressure exceeds a predetermined pressure. A/C low pressure switch interrupts the low pressure signal when line pressure drops below a predetermined pressure. When PCM stops receiving the required signals from high or low pressure switches, compressor relay ground circuit is removed, shutting off compressor.
Three HVAC systems are available for this vehicle. Front HVAC system, front HVAC system with auxiliary heater, and front HVAC system with auxiliary HVAC system.
The front main HVAC control assembly contains 3 control knobs. See Fig 1. Blower control switch receives power through HTR-A/C (20-amp) fuse located in instrument panel fuse block. Temperature control switch knob controls temperature actuator door electronically. Mode control knob operates a rotary vacuum switch to control air delivery mode vacuum actuators located in HVAC module.
The auxiliary HVAC module is located in left rear of vehicle. Functions of the auxiliary HVAC control assembly consist of blower speed, temperature control, and upper or lower mode air outlets.
The auxiliary A/C (if equipped) operates in conjunction with main HVAC system. Liquid refrigerant flows through auxiliary evaporator at all times when main control is energized. Until auxiliary HVAC control assembly is set to cold, the cold air inside auxiliary HVAC evaporator case is blocked off. A/C control through rear auxiliary HVAC control assembly is unavailable. Only when main A/C control assembly is on, does auxiliary HVAC evaporator receive cooling.
The auxiliary heater unit operates independently from main HVAC system. The auxiliary blower switch is independent of main system control. Rear blower motor may be operated even when main system is off. A/C operation will not be available and only recirculation of rear air is available.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.