engine ACURA NSX 1991 Service Repair Manual

Radiator and Condenser Fan Controls

Description

Fan control system:

The cooling fan system is comprised of the radiator fan, condenser fan (left and right), engine compartment fan, radiator

fan low relay, radiator fan high relay, condenser fan relay, engine compartment fan relay, radiator fan resistor, radiator

fan control sensor, A/C pressure switch, fan control unit, climate control unit, and ECM.

The fan control unit controls the operation of the radiator fan and condenser fans.

It uses inputs from the radiator fan control sensor and the A/C pressure switches (A and B) in the A/C system to deter-

mine when the fans should run and at what speed.

Additionally, the temperature switch shuts down the A/C system if the engine coolant temperature (ECT) exceeds

266°F (130°C). If the pressure in the A/C system is higher than normal, pressure switch A closes and the fans will run at

high speed only. See the A/C section for the description and specifications of that function.ProCarManuals.com

Radiator an d Condense r Fa n Control s
Engine Compartmen t Fa n Moto r
Tes t (A/T )
1. Disconnec t th e 2- P connecto r fro m th e engin e
compartmen t fa n motor .
2 . Tes t th e moto r b y connectin g batter y powe r t o th e
A terminal , an d groun d t o th e B terminal .
3 . I f th e moto r fail s t o ru n o r doe s no t ru n smoothly ,
replac e it .
Engin e Compartmen t Fa n Moto r
Remova l (A/T )
1. Disconnec t th e 2- P connecto r fro m th e engin e
compartmen t fa n motor .
2 . Remov e th e engin e compartmen t fa n relay, the tes t
tachomete r connector , an d th e engin e wir e harnes s
fro m th e engin e compartmen t fa n shroud .
3 . Remov e th e thre e mountin g bolts .
MOUNTIN G BOL T6 x 1 0 m m12 N- m (1. 2 kg-m , 9 Ib-ft ) TES
T TACHOMETE RCONNECTOR
WASHER(Corrosio nresistant)
ENGIN E COMPARTMEN T
FAN RELA Y
2-P CONNECTO R
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Fan Relay Tests

Check continuity at the relay terminals.

• There should be continuity between the C and D ter-

minals.

• There should be continuity between the A and B ter-

minals when power and ground are connected to the

C and D terminals.

• There should be no continuity between the A and B

terminals when power is disconnected.

• Radiator fan low relay

• Radiator fan high relay

• Condenser fan relay
Engine compartment fan relay (A/T)ProCarManuals.com

Gauge Assembly
Gauge/Terminal Location Index
SRS components are located in this area. Review the SRS component locations, precautions, and procedures in the SRS

section (24) before performing repairs or service.

SPEEDOMETER:

Indicates 60 mph [60km/h] at 1.026 [637]

rpm of the vehicle speed sensor (VSS).
FUEL GAUGE: Gauge test, page 23-134 Sending Unit Test, page 23-135

VOLTAGE METER:
If, with the No. 5 (15 A) fuse

and other gauges

OK, the pointer of the

voltage meter does not move at all,
replace the voltage

meter.

SAFETY INDICATOR SYSTEM:
See page 23-145 ('93-'96) ('91-'92)A/T GEAR POSITION
INDICATOR SYSTEM:
See page 23-156 ENGINE OIL PRESSURE
GAUGE:
Test page 23-137
ENGINE COOLANT TEMPERATURE (ECT) GAUGE:
Gauge Test, page 23-136 Sender Test, page 23-136
TACHOMETER:

Indicates 100 rpm at 300 pulses per minute

of the igniter unit.ProCarManuals.com

Disassembly

NOTE:
Handle the terminals and printed circuit boards carefully to avoid damaging them.
Replace
the
speedometer,
trip
meter,
and
printed
circuit
board
A as a
unit
if any of
them
is
faulty. Replace the tachometer, odometer, and printed circuit board B as a unit if any of them is faulty.

SPEEDOMETER MOUNTING SCREWS (x3) TACHOMETER MOUNTING SCREWS (x3)
VOLTAGE/FUEL GAUGE
MOUNTING SCREWS (x5) ENGINE COOLANT TEMP./ENGINE OIL PRESSURE
GAUGE MOUNTING SCREWS (x6)
HOUSING
ENGINE COOLANT

TEMPERATURE/

ENGINE OIL PRESSURE GAUGE

Test, page 23-136 and 137

SAFETY INDICATOR
MOUNTING SCREWS (x2) SHIFT INDICATOR
TACHOMETER

Specification, page 23-121
A/T GEAR POSITION
INDICATOR

See page 23-152 ('94-'96) ('91-'93)


LIGHT HOUSING
ODOMETER
SPEEDOMETER

Specification, page 23-121

TRIP METER FUEL/VOLTAGE GAUGE

Test, page 23-121

and 134

FACE PANEL PRINTED CIRCUIT
BOARD B
BOARD-TO-BOARD

CONNECTOR

PRINTED CIRCUIT
BOARD COVER
PRINTED CIRCUIT
BOARD A
SAFETY INDICATOR

See page 23-145 ('93-'96)('91-'92)

TRIP METER
RESET BUTTON
VISORProCarManuals.com

Engine Coolan t Temperatur e (ECT ) Gaug e
ECT Gaug e Tes t
1. Befor e testing , chec k th e No . 5 (1 5 A ) fus e i n th e
under-das h fus e box .
2 . Mak e sur e th e ignitio n switc h i s OFF , the n discon -
nec t th e YEL/GR N wir e fro m th e EC T sendin g uni t
an d groun d i t wit h a jumpe r wire .
YEL/GR NWIRE
ECT SENDIN G
UNI T
3. Tur n th e ignitio n switc h O N (II) .
Chec k tha t th e pointe r o f th e EC T gaug e start s mov -
in g towar d th e "H " mark .
CAUTION : Tur n th e ignitio n switc h OF F befor e th e
pointe r reache s th e "H " mar k o n th e gaug e dial ; i f
yo u don't , yo u ma y damag e th e gauge .
• I f th e pointe r o f th e gaug e doe s no t swin g a t all ,
chec k for :
— A n ope n in th e YE L o r YEL/GR N wire .
— Replac e th e EC T gaug e if th e fus e an d wirin g
is OK .
• I f th e EC T gaug e is OK , chec k th e sendin g unit .
ECT Sendin g Uni t Tes t
1. Disconnec t the YEL/GR N wire fro m the sendin g unit,
and wit h th e engin e cold , us e a n ohmmete r t o meas -
ure resistanc e betwee n th e positiv e termina l an d th e
engin e (ground) .
2 . Chec k th e temperatur e o f th e coolant .
3 . Ru n th e engine , an d measur e th e chang e i n resis -
tanc e wit h th e engin e a t operatin g temperatur e
(radiato r fa n come s on) .
4 . I f th e reading s yo u ge t ar e substantiall y differen t
fro m th e specification s above , replac e th e EC T send -
ing unit .
YEL/GR NWIRE
POSITIV E
• TERMINA L
EC T SENDIN G
UNI T
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Engine Oi l Pressur e Gaug e
Gauge Tes t
1. Befor e testing , chec k th e No . 5 (1 5 A ) fus e i n th e
under-das h fus e box .
2 . Mak e sur e th e ignitio n switc h i s OFF , the n discon -
nec t th e 2- P connecto r fro m th e engin e oi l pressur e
sending unit , an d groun d it wit h a jumpe r wire .
BLU/WH T WIR E
ENGIN E OI L PRESSUR EGAUGE SENDIN G UNI T
3. Tur n th e ignitio n switc h O N (II) .
Chec k tha t th e pointe r o f th e engin e oi l pressur e
gaug e start s movin g towar d th e "8 " mark .
CAUTION : Tur n th e ignitio n switc h OF F befor e th e
pointe r reache s th e "8 " mar k o n th e gaug e dial ; i f
yo u don't , yo u ma y caus e damag e t o th e gauge .
• I f th e pointe r o f th e gaug e doe s no t mov e a t all ,
chec k for :
- A n ope n i n th e YE L o r BLU/WH T wire .
— Replac e th e engin e oi l pressur e gaug e i f th e
wirin g is OK .
• I f th e engin e oi l pressur e gaug e i s OK , g o o n t o
ste p 4 .
4 . Chec k th e engin e oi l pressur e (se e sectio n 8 ).
• I f th e engin e oi l pressur e i s OK , replac e th e en -
gin e oi l pressur e sendin g unit .
Engin e Oi l Pressur e
Warnin g Syste m
Engine Oi l Pressur e Switc h Tes t
1. Rais e th e car , an d plac e safet y stand s in th e prope r
location s (se e sectio n 1 ).
2 . Remov e th e righ t rea r tire .
3 . Remov e th e YEL/RE D wir e fro m th e engin e oi l pres -
sur e switch .
ENGINE OI L PRESSUR E SWITC H
CRANKSHAF TPULLEY
4. Chec k continuit y betwee n th e positiv e termina l an d
engin e (ground ) wit h th e engin e off .
• I f ther e i s n o continuity , th e switc h i s OK .
• I f ther e i s continuity , d o no t replac e th e switch ;
firs t chec k othe r possibl e cause s i n ste p 6 .
6 . Mak e sur e engin e oi l leve l i s OK , the n chec k engine
oi l pressur e (se e sectio n 8 ).
• I f engin e oi l pressur e is OK , replac e th e engin e oi l
pressur e switch .
• I f oi l pressur e i s low , remove , inspect , and , i f
necessary , replac e th e oi l pum p (se e sectio n 8 ).
YEL/RE DWIRE
POSITIV E TERMINA L
OIL FILTE R
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Safety Indicator

Component Location index

SRS components are located in this area. Review the SRS
component locations, precautions, and procedures in the
SRS section (24) before performing repairs or service.
SAFET
Y
INDICATOR (In the gauge assembly)

Removal, page 23-129 ('93-'96) ('91-'92)

Troubleshooting, page 23-152 ('94-'96) ('91-'93)
Input Test, page 23-150 ('94-'96) ('93) ('91-'92)

CEILING LIGHT

Test, page 23-201
ROOF LOCK SWITCH ( * 1)

Test, page 23-154 ('94-'96) ('91-'93)

PASSENGER'S DOOR SWITCH

Test, page 23-204
HIGH MOUNT BRAKE LIGHT

Test, page 23-211

BRAKE SWITCH

Test, page 23-211

DRIVER'S DOOR SWITCH

Test, page 23-204

ROOF HOLDER SWITCH (* 1)

Test, page 23-155 ('94-'96) ('91-'93)

ENGINE COMPARTMENT LID SWITCH

Test, page 23-325 ('93-'96) ('91-'92)
LEFT BRAKE LIGHT
FAILURE SENSOR

Test, page 23-153
TRUNK LATCH SWITCH

Test, page 23-205
RIGHT BRAKE LIGHT

FAILURE SENSOR

Test, page 23-153

*1: NSX-T (open top) only

Description

Safety Indicator System: LED's are used to indicate when the trunk lid, engine compartment lid, a door, or the roof is not latched, or when a brake
light is faulty, or when the roof is not stored or improperly stored in its holder. The LED's will go on and stay on for about
two seconds after the ignition switch has been turned ON, to show that the system circuit is functioning.

Brake Light Bulb Failure Indicator:

If all brake light bulbs are OK, the indicator light stays off because the ORN/WHT wire is grounded by the two brake light
failure sensors connected in series. With the brake lights off, the ground is provided through the diode, the failure sensor relay coil, and bulb filaments. With the brake light on, all four relays (two in the left sensor, two in the right sensor), con-
nected in series, supply ground. If any of the four bulbs is not working, the chain is broken and the ORN/WHT wire is not
longer grounded. The indicator light comes on.ProCarManuals.com

Roof Holder Switch Test

1. Open the rear hatch and engine cover.

2. Disconnect the 1- P connector from the roof holder

switch.

3. There should be continuity between the A and B ter-

minals with the switch released (roof not stored).

4. There should be no continuity with the switch

pushed (roof stored).

Roof not stored (ON)

Roof stored (OFF)ProCarManuals.com

A/T Gear Position Switch

Replacement

SRS components are located in this area. Review the
SRS component locations, precautions, and procedures
in the SRS section (24) before performing repairs or ser-

vice.

1. Remove the console, then disconnect the 12-P and 2-P connectors from the A/T gear position switch.
SWITCH SLIDER (In )

PIN

A/T GEAR POSITION SWITCH
2. Remove the two position switch mounting bolts. 3. Position the slider on the new switch to as shown

above.
4. Shift the shift lever to , then slip the switch into
position,
5. Attach the switch with the two bolts. 6. Test the switch in the and positions. You
should be able to start the engine with the shift lever in position anywhere in the range of free
play.
7. Connect the 12-P and 2-P connectors, clamp the harness, and install the console. Bulb Replacement
SRS components are located in this area. Review the
SRS component locations, precautions, and procedures in the SRS section (24) before performing repairs or ser-

vice.

1. Remove the gauge assembly (see page 23-126).
2. Disassemble the gauge assembly (see page 23-129

('93-'96) ('91-'92)).

3. Remove the bulb from printed circuit board B.
PRINTED CIRCUIT

BOARD B

BULB (1.12 W)

4. Install the indicator in the reverse order of removal.ProCarManuals.com