DESCRIPTION
| WARNING | To avoid injury from accidental air bag deployment, read and carefully follow all SERVICE PRECAUTIONS and DISABLING & ACTIVATING AIR BAG SYSTEM procedures in AIR BAG SYSTEM SAFETY article in GENERAL SERVICING. |
The automatic A/C-heater system is basically a standard A/C-heater system with added electronically-controlled components to provide automatic temperature control. The A/C-heater system is controlled by the Electronic Automatic Temperature Control (EATC) unit.
The EATC unit, built into A/C-heater control panel, uses selected temperature, mode switch position, and inputs from 5 sensors to control discharged air temperature, airflow volume, and outlet vent distribution.
Sensor inputs include signals from ambient air temperature sensor, in-vehicle temperature sensor, engine coolant ambient temperature sensor, sunload sensor, and Potentiometer Balance Resistor (PBR) door motor feedback sensor. The EATC unit includes a self-diagnostic feature. All models are equipped with front A/C system. Some models are equipped with a rear A/C system.
Normal Operation
Fan speed is controlled by front blower speed control unit based on EATC signal. Front blower speed control unit amplifies EATC signal and applies between 4.5 volts (lowest speed) and 12 volts (highest speed) to front fan motor. EATC determines airflow volume based on PBR, in-vehicle temperature sensor, sunload sensor, ambient air temperature sensor, and engine coolant temperature sensor. Fan speed is automatically controlled when EATC system is set to AUTO mode. Blower speed control unit is located at base of front intake unit, next to front blower motor. (Схема №3)
EATC SYSTEM OPERATIONAL CHECK
This check confirms proper operation of fan (blower) motor, mode (discharge air) door, MAX A/C (intake/recirculated air) door, temperature increase and decrease, A/C switch, A/C compressor, automatic mode, memory function and rear blower motor (if equipped).
Conditions For EATC System Operational Check
Start engine and allow to idle at normal operating temperature. Perform operational checks in order listed. Cooling fan will operate at low speed when a normal operating temperature of approximately 203°F (95°C) is attained.
Noisy Blower Motor Operation
Operate blower motor at all speeds, modes, and temperature settings. If noise is constant, check blower motor and fan for debris and/or excessive wear. If noise is intermittent, check air ducts for debris, obstructions and/or air leaks. Perform repairs as necessary.