Air conditioning is switched on by push-button located in center of control panel. see scheme 1 The A/C system will operate only at temperatures greater than 37°F (3°C) with engine on. At least one air outlet must be open when operating A/C system, to prevent evaporator freeze-up.
Driver's and passenger's side blower control buttons allow volume of air entering passenger compartment to be varied. see scheme 1 Airflow increases as "+" is depressed, and decreases as "-" is depressed. If "-" position is selected at minimum blower speed, all data disappears from display. Blower, heater, and A/C are deactivated, and flow of outside air is switched off. Rear A/C-heater control panel blower control button functions identically. see scheme 3
Pushing recirculated air button cuts off outside airflow. see scheme 1
Temperature control buttons determine temperature of air entering driver's side or passenger's side. see scheme 1 Pressing left side of button will decrease air temperature. Pressing right side of button will increase air temperature. Driver and front passenger can select individual temperature ranges. Rear A/C-heater control panel temperature control button functions identically. see scheme 3
This system uses warmth stored in the engine to continue heating the interior after ignition is switched off. see scheme 1 This function can only be activated when ambient (outside) air temperature is less than 59°F (15°C), engine is at operating temperature, and battery is at full state of charge.
Rear Passenger A/C Control
An optional rear passenger A/C control is available which is mounted in rear of center console. Control panel consists of temperature and airflow display, temperature button, and fan button. see scheme 3
AUXILIARY (CONDENSER) FAN
When the A/C system is turned on, an auxiliary (condenser) fan will be cycled in speed No. 1. If coolant temperature exceed 210°F (98°C), the fan will operate at speed No. 2. Auxiliary (condenser) fan will also operate when evaporator sensor has switched off the compressor because of low evaporator temperatures. (Scheme 38)
When the A/C system has been turned off, 2 temperature switches will activate the auxiliary (condenser) fan to speed No. 1 at 196°F (91°C), and speed No. 2 at 210°F (98°C). Auxiliary (condenser) fan is also activated when an abnormal system pressure is sensed.
Scheme 38
AUXILIARY WATER PUMP
An auxiliary (electric) water pump is installed in the water inlets of the heater cores. (Scheme 39) This ensures a sufficient water flow rate through the heater cores even at low engine speeds. Water pump operation is determined by the positions of left and right temperature control wheels. When temperature control wheels are positioned 30 percent from the maximum cool position, water pump is turned on. When temperature control wheels are positioned 25 percent from the maximum cool position, water pump will shut off.
Scheme 39
COLD START ARREST
When starting a cold engine, the cold start arrest automatically controls the air distribution flaps to full defrost position to prevent drafts inside the passenger compartment. Blower runs with a minimum voltage of 3 volts, and the A/C compressor and auxiliary water pump are switched off.
EVAPORATOR TEMPERATURE SENSOR
After A/C button is pushed, compressor is controlled by an evaporator temperature sensor, which will switch the compressor off once evaporator temperature falls to less than 35°F (1.6°C). This prevents evaporator freezing. When evaporator temperature reaches more than 37°F (2.7°C), compressor is turned on.
HEATER CORE SENSORS
The heater core sensors are located near heater core. These sensors constantly monitor heater core temperature. The auxiliary control circuits use signals from sensors to regulate temperature.
INSIDE TEMPERATURE SENSOR
The inside temperature sensor, located in the control panel, must be ventilated to measure actual inside temperature. see scheme 1 Ventilation is accomplished with a radial-type blower (located in rear section of control panel).
OUTSIDE TEMPERATURE SENSOR
Outside temperatures are monitored by an outside sensor, located in the air inlet opening for the blower. This sensor (a resistor) is attached to right side of inlet opening.
Outside sensor causes a slight increase in passenger compartment temperature by switching the inside temperature a few degrees above current outside temperature. If outside temperature is 32°F (0°C), inside temperature is increased about 9°F (13°C). If outside temperature is 68°F (20°C), inside temperature is increased about 2°F (17°C).
High-Pressure Switch
High-pressure switch (located on receiver-drier) disengages compressor clutch when system pressures have increased to 441 psi (31 kg/cm 2 ). Compressor will reactivate when system pressures have decreased to 338 psi (23 kg/cm 2 ).
Low-Pressure Switch
Low-pressure switch (located on receiver-drier) disengages the compressor clutch when system pressures have decreased to less than 17 psi (1.2 kg/cm 2 ). Compressor will reactivate when system pressures have increased to 32 psi (2.2 kg/cm 2 ).
Medium-Pressure Switch
Depending upon system pressures, a medium pressure switch causes the auxiliary (condenser) fan to operate in speed No. 2 when system pressures are at 257 psi (18 kg/cm 2 ). Auxiliary (condenser) fan operation will shut off when system pressures stabilize at 213 psi (15 kg/cm 2 ).
WATER VALVES
Two electromagnetic water valves control the water flow rate through the heater cores. (Scheme 39) Both valves are operated by ground pulses from the A/C-heater control unit. Each valve is spring-loaded open and powered closed for safety reasons. When the driver's side temperature control wheel is in either the maximum heating or minimum cooling positions, it has priority over the passenger's side temperature control wheel position. This is accomplished through electronics in the A/C-heater control unit and final stage switch, which is part of the circuit.
INSTRUMENT PANEL
| WARNING | To avoid injury from accidental air bag deployment, for 1998 vehicles, read and carefully follow all SERVICE PRECAUTIONS and DISABLING & ACTIVATING AIR BAG SYSTEM procedures in AIR BAG RESTRAINT SYSTEM article. For 1999 vehicles, see AIR BAG SAFETY PRECAUTIONS and DISABLING & ACTIVATING AIR BAG SYSTEM procedures in AIR BAG RESTRAINT SYSTEM article. |