1997 ACURA NSX sensor

Sunlight Sensor

Removal

Protect the dashboard with a shop towel, then with a

small screwdriver, carefully pry the sunlight sensor out

of the dashboard and disconnect its connector.

SUNLIGHT

SENSOR
Test

Measure the voltage between the terminals with the sen-

sor out of direct sunlight.

• With the connector connected (probe the back of it):

1.4 ± 0.2 V

• With the connector disconnected: 0.1 - 0.2 VProCarManuals.com

Heater Core Temperature Sensor

Removal

Disconnect the connector, remove the clamp and the

heater core temperature sensor.

CLAMP

HEATER CORE

TEMPERATURE

SENSOR
Compare the resistance reading between the terminals

of the heater core temperature sensor with specifica-

tions shown in the following graph: It should be within

specification.

NOTE: Dip the sensor in ice water, and measure the

resistance. Then pour hot water on the sensor, and

check for change in resistance.
Test

CAUTION: The sensor uses a thermistor which

can be damaged if high current is applied to it

during testing. Therefore, use a circuit tester

that puts out a measuring current of 1 mA or

less.ProCarManuals.com

Evaporator Temperature Sensor
Removal
Give th e evaporato r temperatur e senso r a quarte r turn ,
then pul l ou t t o remov e it .
EVAPORATO RTEMPERATUR E SENSO R
Test
Compar e th e resistanc e readin g betwee n th e terminal s
of th e evaporato r temperatur e senso r wit h specificatio n
shown i n th e followin g graph : I t shoul d b e withi n
specification .
NOTE : Di p th e senso r i n ic e water , an d measur e th e
resistance . The n pou r ho t wate r o n th e sensor , an d
chec k fo r chang e i n resistance .
CAUTION : Th e senso r use s a thermisto r whic h
ca n b e damage d if hig h curren t i s applie d t o it
durin g testing . Therefore , us e a circui t teste r
tha t put s ou t a measurin g curren t o f 1 m A o r
less .
ProCarManuals.com

11. Disconnec t th e connector s fro m al l th e contro l
motors an d sensor s attache d t o th e heater -
evaporato r unit .
1 2 . Remov e th e tw o mountin g bolt s an d tw o nuts , the n
remov e th e heater-evaporato r uni t throug h th e
passenge r door .
CORROSIO N RESISTAN TBOLTHEATER-EVAPORATO R UNIT
NUT S29 N- m (3. 0 kgf-m ,
2 2 Ibf-ft )
6 x 1. 0 m m9.8 N- m (1. 0 kgf-m , 7. 2 Ibf-ft )
13. Instal l th e heater-evaporato r uni t i n th e revers e
orde r of removal , and :
• I f you'r e installin g a ne w evaporator , ad d
refrigeran t oi l (ND-OI L 8 ) se e pag e 22-69 ).
• Replac e O-ring s wit h ne w one s a t eac h fitting ,
and appl y refrigeran t oi l t o them .
NOTE : B e sur e t o us e th e righ t O-ring s fo r
R-134 a t o avoi d leakage .
14. Fil l th e radiato r an d reservoi r tan k wit h th e prope r
engine coolan t mixture . Blee d th e ai r fro m th e cool -
in g syste m (se e sectio n 10 ).
CAUTION : Follo w th e sequenc e describe d in th e ai r
blee d procedure . I f you don't , yo u ma y leav e ai r i n
th e syste m whic h coul d damag e th e engine .
15. I f necessary , adjus t th e heate r valv e cable :
• Se t th e ai r mi x contro l moto r a t COO L positio n
(se e pag e 22-57 ).
• Connec t th e en d o f th e heate r valv e cabl e t o th e
heate r valv e arm .
• Gentl y slid e th e cabl e oute r housin g bac k fro m
the en d enoug h to tak e u p an y slac k in th e cable ,
but no t enoug h t o mak e th e othe r en d mov e th e
ar m o n th e ai r mi x contro l motor . The n sna p th e
clam p dow n ove r th e cabl e housing .
CLAMP
HEATE R VALV EARM
HEATE R VALV ECABLE
16. Tur n th e blowe r on , an d mak e sur e tha t ther e is n o
air leakage .
1 7 . Charg e th e syste m (se e pag e 22-91 ), an d tes t per -
formanc e (se e pag e 22-70 ).
SR S UNI T
ProCarManuals.com

Description ——————————————————\
——————————————————\
———
Ignition Timin g Control :
Th e programme d ignitio n use d i n thi s engin e provide s optimu m contro l o f ignitio n timing . A microcompute r determine s
th e timin g i n respons e t o engin e spee d an d manifol d vacuu m pressure . Th e inpu t signal s ar e transmitte d b y th e crank -
shaf t position/cylinde r positio n (CKP/CYP ) sensor , throttl e positio n (TP ) sensor , EC T sensor , an d MA P sensor . Thi s sys -
tem , no t dependen t o n a governo r o r vacuu m diaphragm , i s capabl e o f settin g lea d angle s wit h complicate d characteristic s
whic h canno t b e provide d b y conventiona l governor s o r diaphragms .
Basi c Contro l
Determinatio n of ignitio n timing/curren t duration :
Th e EC M ha s store d withi n i t th e optimu m basi c ignitio n timin g fo r operatin g condition s base d upo n engin e spee d an d in -
tak e manifol d pressure . Wit h compensatio n b y signal s fro m sensors , th e syste m determine s optimu m timin g fo r ambien t
condition s an d send s voltag e pulse s t o th e ICM .
Compensatio n o f Ignitio n Timing :
Compensatio n Ite m
Idlin g
Compensatio n a t warm-u p
Engin e coolan t
temperatur e compensatio nRelate
d Senso r an d Informatio n
CKP/CY P sensor , MA P senso r
Engin e coolan t temperatur e
(ECT) senso r
ECT senso r Descriptio
n
Ignitio n timin g i s controlle d t o th e targe t spee d
wit h compensatio n accordin g t o th e idlin g speed .
La g angl e i s adjuste d accordin g t o warm-u p con -
dition s t o brin g abou t a goo d balanc e betwee n
operatin g performanc e an d exhaus t ga s level .
Compensatio n fo r lea d angl e a t low coolan t
temperatur e an d la g angl e a t hig h coolan t
temperature .
Contro l a t Star t
Ignitio n timin g is fixe d a t 5 ° BTD C fo r cranking . Th e crankin g is detecte d b y th e CY P senso r (crankin g rpm ) an d starte r signal .
Misfirin g Detectio n
A s par t o f th e OB D II misfirin g detectio n system , eac h o f th e ignitio n coil s ha s a built-i n spar k plu g voltag e sensor . Thi s
senso r detect s th e lon g duratio n hig h voltag e whic h occur s i n cas e o f unfavorabl e combustio n o r misfiring . (Fo r details ,
se e sectio n 11 .)
ProCarManuals.com

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 and Condenser Fan Controls

Control Unit Terminals

THROTTLE VALVE CONTROL

MOTOR RELAY

Wire

Terminal Color
Connects to

1

2

3

4

5

6

7

8

9

10

11

12
-

LT GRN

GRY/BLK

BLU/RED

BLK

BRN/BLK

GRN

—

ORN/BLU

BLU/BLK

YEL/BLK

GRN/BLK
Not used

Radiator fan control sensor

Climate control unit

Radiator fan high and engine

compartment fan relays coil

Ground (G401, G402, G403)

A/C triple pressure switch A

Radiator fan control sensor

Not used

Condenser fan relay coil

ECM
(ACS)

IG2 (Power supply)

Radiator fan low relay coil
1. Disconnect the 3P connector from the resistor.

3P CONNECTOR
RADIATOR

FAN

RESISTOR

NOT USED

2. Using an ohmmeter, measure resistance between

the A and B terminals. Replace the resistor if the

resistance is not within specifications.

NOTE: Resistance will vary with the resistor

temperature; specifications are at 68°F (20°C).

Radiator Fan Resistor

Resistance: 0.54—0.66 ohms
Radiator Fan Resistor TestProCarManuals.com

Radiator an d Condense r Fa n Control s
Radiator Fa n Contro l Senso r Tes t
NOTE : Blee d ai r fro m th e coolin g syste m afte r install -
in g th e radiato r fa n contro l senso r (se e sectio n 10 ).
1 . Remov e th e radiato r fa n contro l senso r fro m th e
thermosta t cover .
2 . Suspen d th e radiato r fa n contro l senso r i n a con -
taine r o f coolan t a s shown .
THERMOMETE R
RADIATOR FA N
CONTRO L SENSO R
ENGIN E
3. Hea t th e coolant , an d chec k coolan t temperatur e
wit h a thermomete r (se e tabl e below) .
4 . Measur e th e resistanc e betwee n th e A an d B ter -
minal s accordin g t o th e table .
5 . I f unabl e t o obtai n th e abov e readings , replac e th e
radiato r fa n contro l sensor .
ProCarManuals.com