DESCRIPTION
All A/C-heating functions are controlled automatically by an Electronic Control Unit (ECU) located within the A/C-heater control assembly. Manual controls allow the driver to select air distribution mode and desired temperatures. In addition to normal A/C system components, the system includes various servomotors, controls, and sensors. (Scheme 3) The system has self-diagnostic capabilities.
Scheme 3
A/C-HEATER CONTROL ASSEMBLY OPERATION
The A/C-heater control assembly consists of a liquid crystal display and various buttons to activate A/C system, set desired temperatures, direct discharged air to appropriate vents, activate defoggers, and control blower fan speed. Separate temperature control switches provide independent left and right temperature control. (Scheme 4)
Scheme 4
SENSORS OPERATION
Resistance of all temperature sensors decreases as temperature increases. Solar sensor resistance is infinite (no continuity) when no light is directed at sensor. When sensor is subjected to bright light, resistance is approximately 4000 ohms. As light intensity decreases, solar sensor resistance increases.
PRESSURE SWITCH OPERATION
Pressure switch protects A/C system from high pressure due to restriction, overcharge, or compressor malfunction. If excessively low or high pressure is sensed within the system, pressure switch inhibits compressor clutch engagement.
AIR INLET DOOR SERVOMOTOR OPERATION
Air inlet door servomotor is mounted on blower unit. Servomotor positions air inlet door so air is drawn from either inside (recirculated air) or outside (fresh air).
AIR MIX DOOR SERVOMOTORS OPERATION
Air mix door servomotors are mounted on both sides of heater unit. Servomotors position air mix door so air is drawn either through heater core or evaporator. Servomotor rotation is transferred to a link which moves air mix door.
AIR VENT MODE DOOR SERVOMOTORS OPERATION
Air vent mode door servomotors are mounted on heater unit. Servomotors rotate so air is discharged from appropriate outlets set by A/C-heater control assembly. Servomotor rotation is transferred to a link, which moves mode door.
MAXIMUM COOL DOOR SERVOMOTORS OPERATION
Maximum cool door servomotors are mounted on heater unit. Servomotors cause extra air to be discharged into vehicle. Servomotor rotation is transferred to control plates, which move the maximum cool doors.
Cooling Fan Motor Operational Check
Connect battery voltage to cooling fan motor terminal No. 2 (Red wire). Connect terminal No. 1 (Black wire) to ground. Cooling fan should run smoothly. Replace cooling fan motor if it does not operate smoothly.
