NISSAN PICK-UP 1999 Repair Manual

ELECTRICAL COMPONENTS INSPECTION
Fan switch
Check continuity between terminals at each switch position.
Knob position Continuity between terminals
OFF
1
V24V26V25
2V23V26V25
3V22V26V25
4V21V26V25
A/C switch
Check continuity between terminals at each switch position.
Switch condition Terminal No.
Continuity
A/C
Å@
ON
V13V12Yes
OFF No
A/C relay
Check continuity between terminal Nos.V3andV5.
Conditions Continuity
12V direct current supply between terminal Nos.
V1andV2Yes
No current supply No
If NG, replace relay.
Thermal protector (For DKV-14C)
Temperature of compressor
ÉC (ÉF)Operation
Increasing to approx. 145 - 155 (293 - 311) Turn OFF
Decreasing to approx. 130 - 140 (266 - 284) Turn ON
SHA157F
RHA362GA
SEF090M
AHA849
TROUBLE DIAGNOSESMANUAL
Magnet Clutch (Cont'd)
HA-2021

Triple-pressure switch
TerminalsHigh-pressure side line
pressure
kPa (bar, kg/cm2, psi)Operation Continuity
Low-pres-
sure side
V1-V4
Increasing to
152.0 - 201.0
(1.520 - 2.010,
1.55 - 2.05, 22.0 - 29.2)ON Exists.
Decreasing to
152.0 - 201.0
(1.520 - 2.010,
1.55 - 2.05, 22.0 - 29.2)OFFDoes not
exist.
Medium-
pressure
side*
V2-V3
Increasing to
1,422 - 1,618
(14.22 - 16.18,
14.5 - 16.5, 206 - 235)ON Exists.
Decreasing to
1,128 - 1,422
(11.28 - 14.22,
11.5 - 14.5, 164 - 206)OFFDoes not
exist.
High-pres-
sure side
V1-V4
Decreasing to
2,059 - 2,256
(20.6 - 22.6,
21 - 23, 299 - 327)ON Exists.
Increasing to
2,648 - 2,844
(26.5 - 28.4,
27 - 29, 384 - 412)OFFDoes not
exist.
*: For cooling fan motor operation
Thermo control amp.
Evaporator outlet air temperature
ÉC (ÉF)Thermo amp.
operationTester
Decreasing to 0.1 - 0.9 (32 - 34) Turn OFF Approx. 12V
Increasing to 2.5 - 3.5 (37 - 38) Turn ON Approx. 0V
Thermo switch
Water tempera-
ture
ÉC (ÉF)Terminal No.
Continuity
Å@
Over 105 (221)
V1V2
No
Less than 100
(212)Yes
RHA364GA
RHA365GA
SHA355F
TROUBLE DIAGNOSESMANUAL
Magnet Clutch (Cont'd)
HA-2022

Introduction
The Automatic Temperature Control (ATC) system provides automatic regulation of the vehicles interior
temperature. The operator selects ªset temperatureº, on which the regulation is based, regardless of the
outside temperature changes. This is done by utilizing a microcomputer, also referred to as the automatic
amplifier, which receives input signals from several sensors. The automatic amplifier uses these input sig-
nals (including the set temperature) to automatically control the ATC system's outlet air volume, air tem-
perature and air distribution.
Features
Air mix door control
The air mix door is automatically controlled so that in-vehicle temperature will reach, and be maintained at
the operator selected ªset temperatureº. For a given set temperature, the air mix door position will depend
on: Ambient temperature, in-vehicle temperature, amount of sunload, and intake air temperature.
Fan speed control
Blower speed is automatically controlled based on temperature setting, ambient temperature, in-vehicle
temperature, intake air temperature, amount of sunload and air mix door position.
With FAN switch set to ªAUTOº, the blower motor starts to gradually increase air flow volume.
When engine coolant temperature is low, the blower motor operation is delayed to prevent cool air from
flowing.
Intake door control
The intake door position will be determined by: Ambient temperature, in-vehicle temperature, and whether
the compressor is on or off.
Outlet door control
The outlet door position will be determined by: Ambient temperature, in-vehicle temperature, intake air
temperature, and amount of sunload.
Magnet clutch control
The compressor operation (ON-OFF) is automatically controlled by the ambient sensor to prevent compres-
sor damage in very cold ambient temperatures.
Self-diagnostic system
The self-diagnostic system consists of five steps. Each step can be accessed by pushing the switches on
the automatic amplifier.
Memory function
With ignition switch turned OFF, the auto amplifier stores in memory the set temperature and inputs of vari-
ous switches. When the ignition switch is turned ON, the system begins operation with the information stored
in memory. The system, then immediately compensates for the actual operating conditions.
DESCRIPTIONAUTO
HA-2023

Overview of Control System
The control system consists of input sensors, switches, the auto-
matic amplifier (microcomputer) and outputs. The relationship of
these components is shown in the diagram below:
Control Operation
RHA467H
RHA468H
DESCRIPTIONAUTO
HA-2024

Display screen
Displays the operational status of the system.
AUTO switch
The compressor, intake doors, air mix door, outlet doors, and blower speed are automatically controlled so
that the in-vehicle temperature will reach, and be maintained at the set temperature selected by the opera-
tor.
Temperature dial (Potentio Temperature Control)
Increases or decreases the set temperature.
OFF switch
The compressor and blower are OFF, the intake doors are set to the outside air position, and the air outlet
doors are set to the foot (80% foot and 20% defrost) position.
FAN switch
Manual control of the blower speed. Four speeds are available for manual control (as shown on the display
screen):
low
, medium low, medium high, high
RECIRCULATION switch
OFF position: Automatic control resumes.
ON position: Interior air is recirculated inside the vehicle.
DEFROSTER switch
Positions the air outlet doors to the defrost position. Also positions the intake doors to the outside air posi-
tion.
MODE switch
Control the air discharge outlets.
FRESH switch
OFF position: Automatic control resumes.
ON position: Outside air is drawn into the passenger compartment.
A/C switch
Manual control of the compressor operation. When the A/C switch indicator illuminates, compressor opera-
tion is being carried out.
DESCRIPTIONAUTO
Control Operation (Cont'd)
HA-2025

Component Location
RHA469H
TROUBLE DIAGNOSESAUTO
HA-2026

Circuit Diagram
HHA187
TROUBLE DIAGNOSESAUTO
HA-2027

Wiring Diagram Ð A/C, A Ð
HHA188
TROUBLE DIAGNOSESAUTO
HA-2028

HHA189
TROUBLE DIAGNOSESAUTO
Wiring Diagram Ð A/C, A Ð (Cont'd)
HA-2029

HHA190
TROUBLE DIAGNOSESAUTO
Wiring Diagram Ð A/C, A Ð (Cont'd)
HA-2030