1999 NISSAN PRIMERA Control

IN-VEHICLE SENSOR
The in-vehicle sensor is attached to the right side of the control
unit. It converts variations in the temperature of the compartment
air drawn in by the aspirator into a resistance value, which is then
input into the auto amplifier.
After disconnecting in-vehicle sensor harness connector, mea-
sure resistance between terminals
p1andp2at sensor har-
ness side, using the table below.
Temperature ÉC (ÉF) Resistance kW
0 (32)6.0
5 (41)4.95
10 (50)3.99
15 (59)3.24
20 (68)2.65
25 (77)2.19
30 (86)1.81
35 (95)1.51
40 (104)1.27
Aspirator
The aspirator is located in front of heater unit. It produces
vacuum pressure due to air discharged from the heater unit,
continuously taking compartment air in the aspirator.
KHA128 PTC Output voltage
Set temperature (ÉC)
Output voltage
NHA295 In-vehicle
sensor
NHA287 In-vehicle
sensor
In-vehicle
sensor
NHA312 Aspirator
duct
Aspirator
SYSTEM DESCRIPTIONAUTO
Control System Input Components (Cont'd)
HA-85

AMBIENT SENSOR
The ambient sensor is located on the hood lock stay. It detects
the ambient temperature and converts it into a resistance value,
which is then input into the auto amplifier.
After disconnecting ambient sensor harness connector, measure
resistance between terminals
p1andp2at sensor harness
side, using the table below.
Temperature ÉC (ÉF) Resistance kW
þ20 (þ4)9.98
þ10 (14)5.57
0 (32)3.26
10 (50)1.98
20 (68)1.25
25 (77)1.00
30 (86)0.81
40 (104)0.54
SUNLOAD SENSOR
The sunload sensor is located on the center defroster grille. It
detects sunload entering through the windshield by means of a
photo diode and converts it into a current value which is then
input to the auto amplifier.
RHA979G Aspirator
Aspirator duct
Heater unit case
NHA313 Ambient sen-
sor
NHA288 Ambient sensor
harness connector
Ambient
sensor
NHA314 Sunload
sensor
SYSTEM DESCRIPTIONAUTO
Control System Input Components (Cont'd)
HA-86

Measure voltage between terminalsp5andp6at auto air con-
ditioner harness side, using the table below.
Input current
mAOutput voltage
V
05.00
0.14.09
0.23.18
0.32.27
0.41.36
0.50.45
lWhen checking sunload sensor, select a place where
sun shines directly on it.
A/C RELAY
The A/C relay is located on the left side of the engine room.
When the A/C remain and fan switch are ON, the A/C relay
operates and transmits A/C operation signals to ECM.
Control System Auto Amplifier (Auto amp.)
The auto amplifier has a built-in microcomputer which processes
the information sent from the various sensors needed for air
conditioner operation. The air mix door motor and blower motor
are then controlled.
Signals from the various switches and the Potentio Temperature
Control (PTC) are directly entered into the auto amplifier.
SUNLOAD INPUT PROCESS
The auto amp. also includes a processing circuit which ªaver-
agesº the variations in detected sunload over a period of time.
This prevents drastic swings in the ATC system operation due to
small or quick variations in detected sunload.
For example, consider driving along a road bordered by an occa-
sional group of large trees. The sunload detected by the sunload
sensor will vary whenever the trees obstruct the sunlight. The
processing circuit averages the detected sunload over a period
of time, so that the (insignificant) effect of the trees momentarily
obstructing the sunlight does not cause any change in the ATC
NHA289 Auto amplifier
Auto amp.
connectorAuto amp.
connector
NHA298
.A/C Relay
RHA024H Auto amplifier
SYSTEM DESCRIPTIONAUTO
Control System Input Components (Cont'd)
HA-87

system operation. On the other hand, shortly after entering a
long tunnel, the system will recognize the change in sunload, and
the system will react accordingly.
SUNLOAD COMPENSATION
The auto amplifier compensates for sunload by altering the air
mix door position and air flow volume according to the amount
of sunload detected by the sunload sensor. When the amount of
sunload is great, the air mix door is moved toward the ªCOLDº
side. Along with this air mix door movement, air flow volume will
also be changed.
YHA296 A/C control panel PTC
In-vehicle sensor
Ambient sensor
Sunload sensorSunload com-
pensation Auto amplifier
Air mix door posi-
tion arithmetic cir-
cuit
Air flow volume
arithmetic circuitAir mix door motor
LOW, MED, HIGH
and AUTO relays
SHA493CA
Air mix door position
compensation amount
Sunload kW (kcal/h, BTU/h)/m2
[kW (kcal/h,BTU/h)/sq ft]
Sunload compensation specifications0.768 (660, 2,619)
[0.0713 (61.31, 243.3)]
SYSTEM DESCRIPTIONAUTO
Control System Auto Amplifier (Auto amp.)
(Cont'd)
HA-88

A/C SWITCH COMPENSATION
The auto amplifier alters the air mix door position and air flow volume according to a signal emitted from the
A/C switch.
When the A/C switch is ªONº, the auto amplifier compensates for the PBR's input signal and moves the air
mix door toward the ªHOTº side.
YHA297 A/C control panel PTC
In-vehicle sensor
Ambient sensor
Sunload sensor
Sunload compensation Auto amplifier
Air mix door position arith-
metic circuit
Output signal pro-
cessAir mix door
motor
PBR
A/C control panel
A/C switch
KHA115
Air mix door opening ratio
(%)
100
15
0
Air mix door position arithmetic value
A/C switchcompensation specifications 0 100 (%)
SYSTEM DESCRIPTIONAUTO
Control System Auto Amplifier (Auto amp.)
(Cont'd)
HA-89

Control System Output Components
AIR MIX DOOR CONTROL (Automatic temperature control)
Component parts
Air mix door control system components are:
1) Auto amplifier
2) Ambient sensor
3) In-vehicle sensor
4) Sunload sensor
5) Air mix door motor (PBR)
6) A/C switch
System operation
The air mix door is automatically controlled so that in-vehicle temperature is maintained to the set tempera-
ture. The temperature set by the PTC (Potentio Temperature Control) and the temperature detected by the
in-vehicle sensor and ambient sensor are compensated by the sunload sensor signal. The auto amplifier then
determines the air mix door position. The air mix door position detected by the PBR is compensated by the
ON-OFF operation of the A/C switch. The air mix door position determined by the auto amplifier is compared
with that detected by the PBR. The auto amplifier then transmits the signal to the air mix door motor in order
to activate it.
KHA116 Auto amplifier
PTC
In-vehicle sensor
Ambient
sensor
sunload
sensor
PBR
A/C switchConstant voltage
transformation
Air mix door posi-
tion arithmetic cir-
cuit
Sunload compen-
sation
Air mix door posi-
tion detection
A/C switch com-
pensationAir mix
door motor
SYSTEM DESCRIPTIONAUTO
HA-90

Air mix door control specifications
SENSOR INPUT PROCESS
The auto amplifier detects the voltage produced by each sensor,
the PBR and fixed resistor. The fixed resistor is built into the auto
amplifier. 12-volt power voltage is first converted to approxi-
mately 5 volts by the constant voltage circuit where it is then
applied to the ground line of the auto amplifier via the fixed
resistor and the sensor. In this manner, the auto amplifier moni-
tors the voltages of the fixed resistor, each sensor and the PBR
to determine sensor input.
SHA497CB A/C switch OFF
A/C switch ON
Voltage (V)
ConditionPTC: 25ÉC (77ÉF)
Fan switch Auto
Withoutsunload
Ambient
temperature ÉC (ÉF)
Air mix door opening angle In vehicle temperature ÉC (ÉF)
0.5 1.0 1.5 2.0 2.5 3.0
PBRresistance (kW)2.4
2.3
2.2
2.1
2.0
1.9
(59) (68) (77) (86) (95) (104)-20 (-4)
-10 (-4)
0 (32)
10(50)
20 (68)
25 (77)
30(86)
40 (104)
54.5
RHA790A Auto amplifier
Constant-voltage
circuit
Fixed resistor
Detection of sen-
sor voltage
Each sensor
SYSTEM DESCRIPTIONAUTO
Control System Output Components (Cont'd)
HA-91

OPERATION OF AIR MIX DOOR MOTOR
lExamplep1
When the temperature in the vehicle is lower than the set
temperature.
When the temperature in the vehicle is low, in-vehicle sen-
sor resistance is great and the input voltage to the auto
amplifier becomes great. As a result, the voltage from the air
mix door position arithmetic circuit also becomes great.
When this voltage is greater than the voltage from the PBR,
comparator (1), Tr
p1and Trp4turn ON.
Accordingly terminal No.
p12becomes!and terminal No.
p13becomes@. The air mix door motor rotates clockwise and
the air mix door moves toward the ªHOTº side.
As the air mix door moves toward the ªHOTº side, the volt-
age from the PBR becomes greater and consequently
becomes equal to that from the air mix door position arith-
metic circuit. As a result, comparator (1) turns OFF and the
air mix door motor stops.
RHA514DB Auto amp.
Comparator
(1)
Air mix door
position arith-
metic circuitAir mix
door
motor
PBR
Comparator
(2)
SHA568CB Auto amp.
Comparator
(1)
Air mix door
position
arithmetic
circuit
PBR
Comparator
(2)Air mix
door
motor
SYSTEM DESCRIPTIONAUTO
Control System Output Components (Cont'd)
HA-92