Electronic Climate Control

Circuit Description
The digital climate control system provides automatic temperature control by measuring interior temperature, comparing it to the desired temperature setting on the control panel, and operating the blower fan and other controls accordingly.

Operating modes:

OFF
- System off
- Fresh air intake closed
- Temperature display off

ECON
- Temperature, blower speed and air distribution controlled automatically
- A/C compressor off

AUTO
- Temperature, blower speed and air distribution controlled automatically
- A/C compressor on

BI-LEV
- Temperature and blower speed controlled automatically
- A/C compressor on
- Air distribution fixed at center and footwell outlets, with a small amount directed to defrost outlets

DEFROST
- Temperature and blower speed controlled automatically
- Air distribution directed to defrost (windshield) outlets

LO/HI
- Overrides automatic control to raise or lower blower speed

The A/C control head is the main control unit for the system. It operates the appropriate system components to control interior temperature based on inputs from the driver and from system sensors. The A/C blower control unit regulates the supply of power to the A/C blower motor (fresh air fan) based on signals received from the control head.

The A/C programmer contains vacuum solenoids that operate vacuum servos to control air distribution and the heater valve. Based on input from the control head, it also actuates the A/C relay to engage the A/C compressor clutch.

The A/C refrigerant low pressure switch opens to interrupt power to the compressor and prevent compressor damage when refrigerant pressure is low.

The A/C refrigerant high pressure cut-out switch provides input to the control head, which will shut off the A/C compressor to prevent damage from overpressure.

Elevated refrigerant pressure closes the refrigerant high pressure switch which operates the second speed of the radiator cooling fan.