engine NISSAN GT-R 1998 Service Manual

FULLY AUTOMATIC AIR CONDITIONER
System Description
The fully automatic air conditioner system utilizes sensors to detect the in-vehicle temperature, ambient
temperature, temperature of air passing through the evaporator, and
sunload. The detected values are
compared with the temperature adjustment dial setting, and calculated by the microcomputer within the
automatic amplifier. The air inlet and outlet temperatures and airflow rate are adjusted in order to main-
@ tain the in-vehicle temperature.
When an abnormal pressure occurs within the cooler cycle [gauge pressure: approx.
2.7 MPa (28 kg/
cm2G)
or higher; or approx. 0.18
MPa
(1.8
kg/cm2-G)
or lower] the refrigerant pressure sensor operates,
Ec
and stops the compressor.
The
ECM turns off the air conditioner relay, and stops the compressor during engine high load.
The blower fan motor utilizes
a brushless motor, and controls the airflow with a built-in IC that recognizes AT
the driver signal (pulse) from the automatic amplifier.
Step-motor type actuators are employed for intake door, mode door, and air mix door. They are rotated in
response to the signal (pulse) step quantity transmitted from the automatic amplifier to control the target
BR
door position.

FULLY AUTOMATIC AIR CONDlTlONER
Component Parts Location
Intake door actua:or
,
Sunload sensor
Controller
B&wer temperature sensor
fan motor
@ Radiator core lower support I
Front defros!er grille (left)
1 ,?efros:er gnlie (left) t I
0 Blower fan motor relay
Engine room, right relay box I / Air conditioner relay I
Blower and cooling unit
I Blower fan motor
? Ar condlboner relay
@ Refrigerant
pressure sensor @ Compressor @ Ambtent sensor
a Liquid tank I @ Englne room. front left
I
Blower and cooling unit
lnta Instrument panel, center I
7 IJj Cluster
lid A 0 Fuse block, rear face 1

FULLY AUTOMATIC AIR CONDITIONER
Performance Test
PROCEDURE
Connect the manifold gauge to the vehicle side cooler cycle (service valve).
Attach a psychrometer to the recirculation air inlet port of the blower and cooling unit (below the glove box);
and attach a dry-bulb thermometer to the right side of the center ventilator grille.
Start and
warm up the engine.
After warming up the engine, check that the engine speed has reached the standard idle speed.
After pressing the AUTO switch, operate the fan switch, mode switch (air outlet switch),
REG switch, tem-
perature adjustment dial and switch; and satisfy the following conditions.
Fan speed: 4th
Air inlet: Recirculation
Air outlet: Ventilator (VENT)
Temperature setting:
18°C
Completely open the hood and all door windows, and close all doors.
Maintain these conditions until the cooler cycle stabilizes. (Approx.
10 minutes)
Maintain the engine speed at idle.
Measure the recirculation inlet temperature and humidity, outlet temperature, and cooler cycle high- and
low-pressures. Compare and judge the values with the "AMBIENT AIR TEMPERATURE AND PRESSURE
CHARACTERISTICS and "INTAKE AIR TEMPERATURE AND DISCHARGE AIR TEMPERATURE CHAR-
ACTERISTICS.

FULLY AUTOMATIC AIR CONDITIONER
Trouble Diagnosis by Self-diagnosis Function
There are 5 steps in the self-diagnosis: to check for any sensor failure, and to check that a given control sig-
nal is transmitted to each output device.
Diagnosis
content
- - -
Diagnostic
item
i Step I I Step 2 - - - - - - - --
Each sensor check
Indicator lamp check
Display segments Ambient sensor
0 Indicator lamp In-vehicle sensor
lntake air tempera-
ture sensor
Sunload sensor Step
3
Each
actuator check
and reset check display for each
sen-
lntake door actuator
Air mix door actua-
tor Mode door actuator
lntake door actuator
Air mix door actua-
tor
Mode door actuator
Blower fan motor
Compressor
Air purifier (only
when connected)
Ambient sensor
In-vehicle sensor
lntake air tempera-
ture sensor
SELF-DIAGNOSIS OPERATION PROCEDURE R8
Switching to self-diagnosis mode
Turn the temperature adjustment dial all the way to the left.
Start the engine with the ignition switch from OFF position. Within 10 seconds, press and hold the OFF
switch for more than approx. 5 seconds, to start the self-diagnosis step 1.
Self-diagnosis completion EL
a Turn the ignition switch OFF.
Turn the AUTO switch ON.
Switching between self-diagnosis steps
Use the temperature adjustment dial to switch between self-diagnosis steps 1 to 5.
Temperature adjustment dial (turn clockwise): Step
1-5
Temperature adjustment dial (turn counterclockwise): Step
5- 1
a Refer to "SELF-DIAGNOSIS DISPLAY ITEM" for the diagnosis contents of each step.

FULLY AUTOMATIC AIR CONDITIONER
Magnet Clutch System Check
MAGNET CLUTCH
Disconnect the compressor connector. Apply approx. 12V to the compressor to check the magnet clutch
operation.
/;sn
AIR CONDITIONER RELAY QJg
Remove the air conditioner relay. Apply approx. 12V between the air conditioner relay terminals No. 1 and
2. Check the relay operation sound. Ec Check the continuity between terminals No. 3 and 5.
REFRIGERANT CHARGE AMOUNT AT
Connect the manifold gauge to the vehicle side service valve.
Check that the lower pressure side (gauge pressure) is more than approx. 0.1 8 MPa (1.8 kg/cm2.G). BR
ECM
Start the engine, and short-circuit the ECM terminal No. 14 to the ground. Check the magnet clutch operation.
INTAKE AIR TEMPERATURE SENSOR
Start the engine, and short-circuit the intake air temperature sensor terminal No. 1 to the ground. Check the Rs
maanet clutch o~eration.
Blower Fan Motor System Check
BLOWER FAN MOTOR
Disconnect the blower fan motor connector. Short-circuit the blower fan motor terminals No. 2 and 5 to El!, (
the ground. Apply approx. 12V to the terminal No. 6, and check the motor operation.
Connect the blower fan motor connector. Turn the ignition switch to the ON position, and change the fan sD
switch from 1st to 4th. Check the blower fan motor terminal No. 5 with an oscilloscope. When the termi-
nal No.
5 is normal according to the following table and the fan airflow does not change, this indicates a
faulty blower fan motor.
When the terminal No.
5 results differ from the following table and the fan airflow does not change, this
indicates either a faulty harness between the blower fan motor and automatic amplifier, or a faulty auto-
matic amplifier.

FULLY AUTOMATIC AIR CONDITIONER
Symptom
Trouble Diagnosis for Each Symptom
No airflow
Airflow does not change. Operation check
Check blower fan motor operation. (Refer to "Blower Fan Motor Sys-
tem Check".)
The above is normal.
I Automatic amolifier 1 Faultv automatic amplifier
Faulty attachment of air mix door
rod, or air mix door lever
Faulty air mix door system
ElG
(damage, lock, etc.)
Malfunctioning unit
Blower fan motor Probable cause
Faulty blower fan motor
Check attachment status of the air
mix door actuator.
Common item (Check and confirm this
item along with the fol-
lowing three items.)
Air mix door
Abnormal display in self-diagnosis
step
3
Check that the air mix door oper-
ates when the temperature
adjust-
ment dial is set to
18OC or 32°C.
Faulty sensor (Refer to 'Component a
Parts Inspection".)
Faulty sensor harness
Air
mix door actuator
Air mix door actuator
Abnormal display in self-diagnosis
step 2
Magnet clutch does not operate
Magnet clutch Refer
to 'Magnet Clutch System R8
with AUTO switch, or A/C switch. Check".
I Faulty
air mix door actuator
Faulty air mix door actuator system AT
hamess
(Refer to "Actuator System Check".)
BW
Refer to "Actuator System Check".
@'i?
Sensor
Tem- perature
control mal-
function No
cool airflow
(Flow amount is normal.)
ngeranr
cnarge
amounr.
( Cooler cycle 2 ~erformance. I Refer to 'Performance Test". I
The above is normal. I Automatic amolifier 1 Faulty automatic amplifier I
After warming up, the heater core
inlet and outlet hoses are not warm. 1 Coolant I
Engine coolant failure
Clogged heater hose or heater core
No warm airflow
(Flow
amount is normal.)
The above is normal. Automatic amplifier
1 Faulty automatic amplifier
Blower fan motor speed does not
change even when the fan switch is Blower fan motor
changed. Refer
to "Blower Fan Motor System
Check".
I
When the fan switch is in 4th, Faulty aspirator
smoke is not drawn in from the
in-
Aspirator Clogged
or disconnected aspirator
vehicle sensor inlet. duct
Large
in-vehicle tem-
perature difference in
relation to temperature
setting Check the setting difference
between the set temperature and
control temperature. Error
in temperature difference set-
ting
- The above isnormal.- Automatic amplifier Faulty automatic amplifier
Faulty attachment of mode door
lock, mode door link, or mode door
Check mode door operation. Mode door lever
Faulty mode door system (damage,
lock, etc.)
Faulty mode door actuator
Abnormal display in self-diagnosis Faulty mode door actuator system
step
3 Mode door actuator
harness (Refer to "Actuator System
Check".)
Air
outlet does not switch.
Normal display in self-diagnosis
Mode door actuator
step
3
Refer to "DOOR ACTUATOR
HARNESS", "Actuator System
Check".
The above is normal.
I Automatic amplifier I Faulty automatic amplifier - - I I Faulty attachment of intake door
Check intake door operation. lntake
door lever
Faulty intake door system (damage,
lock, etc.)
~aulG intake door actuator
Faulty intake door actuator system
hamess (Refer to "Actuator System
Check".)
Abnormal
display in self-diagnosis
door step 3 Air inlet does fiot switch.
Normal display in self-diagnosis
lntake door actuator
step
3
Refer to "DOOR ACTUATOR
HARNESS", "Actuator System
Check".
I I The above is normal. I Automatic amplifier I Faulty automatic amplifier

COMBINATION METER
Trouble Diagnoses (Cont'd)
VEHICLE SPEED INPUT SIGNAL DIAGNOSIS
I Connector
WARNING LAMP CHECK Does ABS warning lamp remain ON with
ignition switch ON?
ABS I
Perform ABS self-diagnosis
and check faulty circuit.
Refer to
BR section ("ABS
SYSTEMn).
Continuity exists.
Terminal No. 19 and ground:
No continuity
. -- I I
HARNESS CHECK ' Disconnect ABS control unit connector
(TK24)
and meter connector (TK20
Brown).
Terminals No. 19 - 24:
OK
El f
Meter control unit connector on vehicle
NG+'
I - = 'ELF0970D
El
@EM
Meter control unit connector on vehicle rn
rm-1 ffee
1
L / - - -
ELFo971D -
ABS control unit to meter
harness is faulty.
Meter control unit
is faulty. VEHICLE SPEED INPUT SIGNAL
CHECK 1 Connect meter connector (TK20 Brown). Terminal No. 19 and around:
'2
" Approx. 9V
OK
r9 v
VEHICLE SPEED INPUT SIGNAL
CHECK 2 Connect ABS control unit connector
(TK24).
Start the engine and drive the vehicle. Terminal No. 19 and ground:
Specification
Refer to "Combination Meter InpuffOutput
Signal Specificationsn on the next page.
OK
Meter control unit is faulty.
5' Pelform ABS self-diagnosis and check faulty circuit.
Refer to BR section ("ABS
SYSTEMn).

COMBINATION METER
Combination Meter
InputlOutput Signal
Specifications
Terminal No. Measuring condition
Signal name
Ignition switch Operation or condition
Disconnect ECM connector. Approx.
8 - 10V
At 2.000 rprn: Approx. 3.OV
IVI
15
10
5 0
ELF0973D
Tachometer drive
signal
Engine is idling or running at
!,000 rpm. RB25DET
At ~dling: Approx. 7.2V At 2.000 rprn: Approx. 72V
(VI
(VI ST
15 I5 10 10
5 5
0 0
RS
ELF0974D RA
Refer to "Component Parts Inspection" (EL-27).
Approx. 12V I
-uel gauge signal
OFF With TCS
Vehicle speed: Approx. 40 km
(VI
15 10 5 0 -5 -1 0 -1 5
A Veh~cle Speed Approx 60 kmh
Body
lrounc
Speedometer is in operation.
Vehicle speed is approx.
10 kmh.)
Vehicle speed is approx.
i0 kmh.)
e speed
inpi
Without
TCS Vehcle speed: Approx. 40 k
IV!
15 10 5 0
h Vehicle speed: Approx. 60 kmh (V) 15 10
5
0
ELF0376D
-
-
;peedometer is not in opera-
on.
hermal
transmitte
iignal Refer
to "Component Parts Inspection"
(EL-27)
gnition power sup
'IY Approx. 12V
Approx. 4.8V or OV
Vehicle speed is approx. 40 kwh: Approx. 2.4V (Vi d!!!!!!!!!] ,
rehicle speed sign 2 pulses) ipeedometer
is in operation.
Vehicle speed is approx.
0 kmm.)
Voltage the
part
of the indicates the value checked with an )gue circuit tester

COMBINATION METER
Component Parts Inspection (Cont'd)
Fuel gauge unit harness
connector
Lower side
<
I
I
I
(Full) Lead switch
harness connector
on fuel gauge unit
h L Upper side
Harness connec:or on lead sw~lch
With fuel
T/f Without fuel
Lower side
(Empty)
FUEL GAUGE UNIT
Remove fuel gauge unit from the vehicle.
Check the gauge resistance on the gauge with the fuel gauge
at Empty and then Full.
SD
LEAD SWITCH
Remove fuel gauge unit from the vehicle.
Check continuity between terminals on the lead switches in the
tank.
Terminal No.
1-3
Termina! No. I Condition I Continuity
Float position
Full
Empty
THERMAL
TRANSMITER
Resistance R
Approx. 6 max.
Approx. 80 min.
5 - 7 6-7
0 When the engine has warmed up to approx. 80°C, measure
resistance between thermal transmitter and body ground.
Specification: Approx. 76 - 90Q
There is no continuity when approx. 26 of fuel is left in the sub fuel tank.
With fuel
Without fuel Yes
No

COMBINATION METER
Component Parts Inspection (Cont'd)
If the measured resistance is out of the specification with the
thermal transmitter on vehicle, remove the thermal transmitter
from the vehicle and measure resistance as
shown left.
Water temperature "C 1 Resistance R
Approx. 60 I Approx. i70 - 21 0
Approx. 65 I Approx. 140 - 170
Approx. 80 I Approx. 76 - 90
I
- - -- Appro~. 100 Approx. 47 - 53
OIL PRESSURE SENSOR (OIL PRESSURE WARNING
LAMP SWITCH)
Check continuity between oil pressure sensor and body ground.
Terminal No.
OIL PRESSURE SENSOR
Engine is stopped.
Engine is started.
Check the resistance between the oil pressure sensor and body
ground.
Condition
Terminal No.
I Oil pressure MPa (kgkmq-1 Resistance R
Oil pressure
MPa (kg/cm2) 1 Continuity
Less than
0.01 - 0.024
(0.1 - 0.25)
More than 0.01 - 0.024
(0.1 - 0.25)
0.2 (2.0) Approx. 37 - 45
Yes
No