Overview of Control System

ATC Control Unit (Auto Amplifier) Switch Functions:

AIR MIX CONTROL
The Air Mix Door is automatically controlled so that in-vehicle temperature is set to a predetermined value based on: temperature setting, ambient temperature, in-vehicle temperature, amount of sunload, and intake air temperature.

FAN SPEED CONTROL
Blower speed is automatically controlled by: temperature setting, ambient temperature, in-vehicle temperature, amount of sunload, intake air temperature, and Air Mix Door position.

INTAKE DOOR CONTROL
The Intake Door is automatically controlled by: temperature setting, ambient temperature, in-vehicle temperature, amount of sunload, and the A/C Compressor's ON-OFF operation.

OUTLET DOOR CONTROL
The Outlet Door is automatically controlled by: temperature setting, ambient temperature, in-vehicle temperature, amount of sunload, and intake air temperature.

COMPRESSOR CLUTCH MAGNET CONTROL
The A/C Compressor operation (ON-OFF) is decided as follows: The Ambient Sensor inputs the ambient temperature into the Auto Amplifier. The Auto Amplifier then signals the Powertrain Management ECM (Nissan ECCS Control Unit) through the Dual-Pressure Switch. The ECM considers the input signal from the Auto Amplifier and turns the Compressor Clutch Magnet ON or OFF. The ECM also considers the input signal from the Throttle Sensor (for acceleration cut-out control) and turns the Clutch Magnet ON or OFF.

RECIRCULATION CONTROL
Pushing the RECIRC switch will cancel all outside air being allowed into the vehicle. The vehicle interior air will be recirculated for approx. ten minutes and then the RECIRC function will be cancelled automatically.

SELF-DIAGNOSTIC SYSTEM
There are five kinds of self-diagnostic systems and one auxiliary check. Each can be accessed by pushing certain switches on the Auto A/C Amplifier (Control Head). Available diagnostic systems are:

Step 1: Checks L.E.D.s and segments
Step 2: Checks each sensor circuit for an open or short
Step 3: Checks mode door position
Step 4: Checks operation of each actuator
Step 5: Checks temperature detected by sensors
Auxiliary Mechanism: Temperature setting trimmer

MEMORY FUNCTION
When the Ignition Switch is turned from ON to OFF, the Auto Amplifier stores the temperature settings and inputs from the various switches in its memory. When the Ignition Switch is turned from OFF to ON, the memory function begins with the inputs stored immediately before the switch was turned OFF.

FRESH VENT
When the Fresh Vent Lever is in the ON position, a small of amount of air flows directly from the evaporator outlet to the face vent duct, bypassing the heater unit. This provides a small amount of cool air to the face vents even though warm air may be discharging through the foot or defroster outlets.