1991 ACURA NSX Service Repair Manual

Radiator an d Condense r Fa n Control s
Componen t Locatio n Inde x
RADIATO R FA NLOW RELA YWire colors : WHT/BLU ,YEL/BLK, RE D an d GRN/BL K
RADIATO R FA N
HIG H RELA Y
Wire colors : WHT/BL UBLK, YEL/BL K an d BLU/RE D
CONDENSE R FA N RELA Y
Wir e colors : WHT/GRN , BL K
YEL/BL K an d ORN/BL U
RIGH T CONDENSE R
FA N MOTO R
Test , pag e 23-11 7
Replacement , se e sectio n 2 2
UNDER-HOO D RELA Y BO X A
RADIATO R FA N
RESISTO RTest, pag e 23-116 ,
A/C TRIPL E PRESSUR E
SWITC H
See sectio n 2 2
LEF T CONDENSE R FA N
MOTO R
Test, pag e 23-11 7Replacement , se e sectio n 2 2
RADIATO R FA N MOTO RTest, pag e 23-11 7Replacement , se e sectio n 5
CLIMAT E CONTRO L UNI TTroubleshooting , se e sectio n 2 2
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THROTTLE VALV E CONTRO L
MOTO R RELA Y
ECM
FAN CONTRO LUNIT
ENGIN E COMPARTMEN T
FA N RELA Y (A/T )
Wir e colors : YEL/BLK ,
BLU/RED , WHT/GRN ,
an d WHT/BL U
Test , pag e 23-11 9
RADIATO R FA N CONTRO L SENSO R
Test, pag e 23-12 0
ENGIN E COMPARTMEN T FA N MOTO R (A/T )Test, pag e 23-11 8Replacement , pag e 23-11 8
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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

Troubleshooting
NOTE: Th e number s i n th e tabl e sho w th e troubleshootin g sequence .
*: Refe r t o sectio n 2 2 fo r A/ C pressur e inspectio n o f th e A/ C system .
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Radiator and Condenser Fan Controls

Control Unit Terminals

THROTTLE VALVE CONTROL

MOTOR RELAY

Wire

Terminal Color
Connects to
1. Disconnect the 3-P connector from the resistor.

RADIATOR

3-P CONNECTOR 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 Test

FAN CONTROL

UNITProCarManuals.com

Radiator Fan Motor Test

1. Disconnect the 2-P connector from the radiator fan

motor.

2. Test the motor by connecting battery power to the

A terminal, and ground to the B terminal.

3. If the motor fails to run or does not run smoothly,

replace it.
Condenser Fan Motor Test

1. Disconnect the 2-P connector from the condenser

fan motor.

NOTE: The illustration shows the right condenser.

2. Test the motor by connecting battery power to the

A terminal, and ground to the B terminal.

3. If the motor fails to run or does not run smoothly,

replace it.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