1991 ACURA NSX Service Repair Manual

Description
Outline
The ai r conditionin g remove s th e hea t fro m th e passenge r compartmen t vi a th e rout e show n below .
Usin g th e refrigeran t (R134a )
Section/compressio n
High temperature /high pressur e ga s
COMPRESSO R I
Radiatio n o f hea t
RIGHT/LEF TCONDENSE R
Less moisturize dlow pressur e vapo r
High temperature / Hig h temperature /high pressur e liqui d Trap s debri s an d act s hig h pressur e liqui das a n accumulator .
RECEIVER/DRYE R
Absorption o f hea t
EVAPORATO R
More liquefie dlow pressur e vapo r
EXPANSIO N VALV E
RECEIVER/DRYE R
RIGHTCONDENSE R EVAPORATO RCOMPRESSOR
LEFTCONDENSE REXPANSIONVALVEHEATE RCORE
This ca r use s HFC-134 a (R-134a ) refrigeran t whic h doe s no t contai n chlorofluorocarbons . Pa y attentio n t o th e followin g
servic e items :
• D o no t mi x refrigerant s CFC-1 2 (R-12 ) an d HFC-134 a (R-134a) . The y ar e no t compatible .
• Us e onl y th e recommende d polyalkyleneglyco l (PAG ) refrigeran t oi l (ND-OI L 8 : P/ N 38899-PR7-A01 ) designe d fo r th e
R-134 a compressor . Intermixin g th e recommende d (PAG ) refrigeran t oi l wit h an y othe r refrigeran t oi l wil l resul t i n
compresso r failure .
• Al l A/ C syste m part s (compressor , discharg e line , suctio n line , evaporator , condenser , receiver/dryer , expansio n valve .
O-ring s fo r joints ) hav e t o b e prope r t o refrigeran t R-134a . D o no t confus e wit h R-1 2 parts .
• Us e a haloge n ga s lea k detecto r designe d fo r refrigeran t R-134a .
• R-1 2 an d R-134 a refrigeran t servicin g equipmen t ar e no t interchangeable . Onl y us e a Recovery/Recycling/Chargin g
Syste m tha t i s U.L.-liste d an d i s certifie d t o mee t th e requirement s o f SA E J221 0 t o servic e R-134 a ai r conditionin g
systems .
• Alway s recove r th e refrigeran t R-134 a wit h a n approve d Recover/Recycling/Chargin g System , befor e disconnectin g
any A/ C fitting .
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A/C Triple Pressure Switch

Construction

The A/C triple pressure switch consists of a High-Low pressure switch (A/C pressure switch A) and a Middle pressure

switch (A/C pressure switch B).

• High-Low pressure switch

If the refrigerant pressure becomes too high (due to blockage), or too low (due to leakage), the A/C triple pressure

switch sends a signal to the fan control unit to prevent the compressor from operating.

Middle pressure switch

If the refrigerant pressure goes above or below 1 550 kPa (15.5 kg/cm2, 220 psi), the A/C triple pressure switch sends

a signal to the ECM, then the ECM operates the idle control.ProCarManuals.com

Description

Fan Control Unit

The fan control unit performs calculations based on signals from the radiator fan control sensor. It them controls the

operation of radiator fan speed (High-Low), engine compartment fan, condenser fan and A/C compressor.

IG2

RADIATOR FAN (Low)

RADIATOR

FAN CONTROL

SENSOR
RADIATOR FAN (High)

ENGINE COMPARTMENT

FAN

CONDENSER FAN

(Right and Left)

ECM
(ACS)

A/C

TRIPLE

PRESSURE

SWITCH

GND

22-8
A/C SWITCHProCarManuals.com

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.

POWER TRANSISTORBLOWER MOTOR

RECIRCULATION

CONTROL
MOTOR

CONDENSER
FAN MOTOR UNDER-HOOD RELAY BOX A
(CONDENSER FAN RELAY, COMPRESSOR CLUTCH RELAY,
BLOWER MOTOR HIGH RELAY, BLOWER MOTOR RELAY)
UNDER-HOOD

FUSE/RELAY

BOX

HEATER CORE TEMPERATURE SENSOR
CLIMATE CONTROL UNIT VENT DOOR
CONTROL MOTOR
OUTSIDE AIR
TEMPERATURE SENSOR ENGINE COMPARTMENT

FUSE/RELAY BOX
A/C TRIPLE PRESSURE SWITCH
FAN CONTROL UNIT (Fan radiator and con-

denser fans inside car,

behind seats)
EVAPORATOR

TEMPERATURE

SENSOR

IN-CAR

TEMPERATURE
SENSOR
MODE CONTROL

MOTOR

AIR MIX CONTROL MOTOR
SUNLIGHT

SENSORProCarManuals.com

Troubleshooting

Self-diagnosis Circuit Check
The Automatic Climate Control System has a built-in self diagnosis feature. To run it, turn the ignition switch ON (II),
then turn the fan speed dial to the AUTO position. Set the temperature control dial to 60° F(18°C), then gradually move

0

th
e
dial up the temperature range to 90°F (32°C). At each temperatu\
re setting, push both the AUTO and OFF burtons
o

n
the control unit at the same time. Wait for at least one minute for the\
system to readjust and check for problems.

If any problems are found in circuits "A" through "I", the system will indicate which circuit has the problem by lighting

the respective indicator light.
NOTE: The climate control unit does not memorize which self-diagnosis indicator lights come on. If you turn the ig-

nition switch OFF, the indicator light memory will be lost.

AUTO BUTTON

OFF BUTTON

TEMPERATURE CONTROL DIAL
TEMP DISPLAY


FAN SPEED DIAL

NOTE:
When you turn the ignition switch OFF, the self-diagnosis function will be canceled. After completing repair work, run the self-diagnosis again to make sure that there are no other malfunctions.COMPONENT WITH PROBLEM
IN-CAR TEMPERATURE SENSOR
OUTSIDE AIR TEMPERATURE

SENSOR

SUNLIGHT SENSOR
HEATER CORE TEMPERATURE

SENSOR

EVAPORATOR TEMPERATURE

SENSOR

AIR MIX CONTROL MOTOR
MODE CONTROL MOTOR
RECIRCULATION CONTROL MOTOR
VENT DOOR CONTROL MOTOR
POSSIBLE CAUSE

Open or short circuit

Open or short circuit

Open or short circuit

Open or short circuit

Open or short circuit

Open or short circuit

Air mix door stuck

Open position signal circuit

Mode door stuck

Open position signal circuit

Open or short circuit

Vent door stuck
Refer to PAGE

22-16

22-1

8

22-20
22-22
22-24
22-2
6
22-28
22-30
22-32
INDICATOR

MODE

A/C
ON
(A/C)

OFF
(A/C)

LED on

defroster

button

A

B

C
D

E

F

G
H
I
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Function Selection and Operation Check

This check will quickly and automatically select and operate all functions of the climate control system, in the combina-

tions and sequence shown below. It may help clarify a problem, or identify one that didn't show up when you perform

the self-diagnosis circuit check.

Turn the FAN switch to AUTO, then push in both the MODE and AUTO buttons and hold them in while you start the

engine. The control unit will then automatically run the check in eight steps, one step every five seconds.

To stop at one of those steps, push the MODE button; to continue, push it again for each step after that.

Pushing the OFF button or turning the ignition OFF, will turn off the check.

Check the temperature, volume, and source of the air flow, and compare it to what the chart shows it should be.ProCarManuals.com

Troubleshooting

Symptom-to-Components Chart

Use this chart if the self-diagnosis checks don't identify any cause for the symptom.
Across each row in the chart, the potential sources of a symptom are ranked in the order they should be inspected in, starting with . Find the symptom in the left column, read across to the most likely source, then refer to the page listed
at the top of that column. If inspection shows the component is OK, try component , etc.

22-34
('93-'96),
22-38
('91-'92
Models)
22-16

22-18

22-20

22-22

22-24

22-26

22-30
('93-'96),22-28

('91-'92
Models)

22-30

('93-'96),

22-32
('91-'92

Models)

22-32

('93-'96),
22-34
('91-'92 Models)
22-36
('93-'96),
22-40
('91-'92 Models)
22-40
('93-'96),
22-46
('91-'92
Models)
22-42
('93-'96),
22-50
('91-'92 Models)
22-44
('93-'96),
22-52
('91-'92
Models)
22-48

PAGE

* Cool down engine coolant, and recheck. (Because the fan control unit turns off the compressor and condenser fan at temperatures above 130°C)ProCarManuals.com

Climate Contro l Uni t Input/Outpu t Signal s
CLIMAT ECONTRO L UNI T
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