1977 DATSUN PICK-UP cooling

MAIN
RELAY

The
main

relay
is
located
on
the

cooling
unit

When
the

ignition
switch
and
fan

switch

are
both
turned
on
the

COll

@

FAN
SWITCH

The

fan
switch

serving
as
a
control

unit
is

installed
on
the
center
console

This
switch

controls
the

blower
motor

speed
through
the
resistor
It
is
also

used
as
a

main

relay
switch

Fig
AC
I0
Fan
switch

THERMO

SWITCH

The
thermo

switch
is

located
on
the

upper
side
of
the

cooling
unit
and
is

controlled

by
the

cable
and
the
con

trollever
attached
to
the
console
box

It
is
so

designed
that
when
the
air

passing

through
the

evaporator
core
is

cooled
down

to
the

predetermined
Air

Conditioning

tacts
in
the

relay
are
closed
Then

electrical

power
from
the

battery
is

supplied
to
the
blower

motor
and
the

electrical
clutch
for
the

compressor

@

Dc

IDe

ID
1
1

l@

@
e

L
J

AC465

Fig
A
C
9
Main

relay

temperature
set

by
the

control
lever

it

automatically
turns

off
When
the

switch
is
turned
off
the

magnetic

clutch
is

turned
off

stopping
the
flow

of

refrigerant
inside
the

cooling
system

and

increasing
the

cooling
system
tem

perature

When
the

air
rises
to
the

pre

determined

temperature
the
thermo

switch

automatically
turns

on
In
this

way
the

temperature
of
the
air
dis

charged
from
the

cooling
unit
is
auto

matically
controlled
as
desired

PRESSURE

SWITCH

The

pressure
switch
is
turned
off

when

refrigerant
pressure
in
the

cooling
system
rises
to

an

abnormally

high
level
28

kg
cm2

398

psi
This

in

turn
turns
off
the

compressor

magnetic
clutch

actuating
the
com

pressor
relay
and

gradually
decreasing

pressure
in
the

cooling
system
When

the

pressure
drops
to
or
below
24

kg
cm2
341

psi
the

pressure
switch

again
turns
on

Thus

cooling

system
refrigerant

pressure
is

automatically
maintained
at

the

proper
value

a
t
all
times

AC
7
COMPRESSOR
RERAY

The

compressor
relay
is

attached
to

the
receiver

dryer
bracket
on
the

right

side

of
the

engine
compartment
This

relay
is

actuated
by
the

fan
switch

thermo
switch

and

pressure
switch
to

turn
on

and
off
the

compressor

magnetic
clutch

cv

1

2

AC731

Fig
A
C

11
Pressure
switch
and

compressor
relay

F
I
C
D
SOLENOID
VALVE

The
F
l
C
D
solenoid

valve
is
at

tached
to
the
dash

panel
in
the

engine

compartment
This
valve

supplies
vacu

um
to
the

F
I

C
D

diaphragm
through

the
vacuum
hose
connected

to
the

engine
intake
manifold
when
the

engine
is

at
idle
and

the

cooling
system

is
ON

thereby
raising
idle

speed
to
the

predetermined
rpm
800

IW

r

e

I

1
s

AC132

Fig
AC
12
F
l
C
D
solenoid

value

Notes

a
The
bubbles
seen

through
the

sight

glass
are
influenced

by
the
ambient

temperature
Since
the
bubbles
are

hard
to
show

up
in

comparatively

low

temperatures
below
200C
6S0

F
it
is

possible
that

a

slightly

larger
amount
of

refrigerant
would

be
filled
if

supplied
according
to

the

sight
glass
Be

sure
to
recheck

the
amount
when
it

exceeds
200C

680F
In

higher
temperature
the

bubbles
are

easy
to

show

up

b

When
the

screen
in
the

receiver

dryer
is

clogged
the
bubbles
will

appear
even
if
the
amount
of

refrig

erant
is
normal
In
this
case
the

outlet
side

pipe
of
the
receiver

dryer
becomes

considerably
cold

PERFORMANCE
TEST

Check
for
the
amount
of

refrigerant

in
the

system
can
be

made

by
meas

uring

pressure
on

discharge
side

The

correct
amount
of

refrigerant
is

in
the

system
if

pressure
on
the

discharge
side
is
within

the

specified

range
For
details
refer
to

Perform

ance

Test
described
later

Overcharging
will
show

up
in

higher

pressure
on
discharge
side

COMPRESSOR
OIL

LEVEL

CHECK

The
oil

used
to
lubricate

compres

sor
circulates
into

system
from
the

oil

sump
while

c9mpressor
is

operating

The

efore
to

correctly
measure
com

pressor
oil
the

amount
of
oil

flowing

to

system
must
be

considered
If
a

considerable
amount
of

leakage
of

refrigerant
gas
happens
the

leakage
of

compressor
oil
is
also
considered

There

will
be

no

compressor
oil
leak

age
from
a

completely
sealed

system

When

system
operates
under

satisfying

condition
the

compressor
oil
level

check
is

unnecessary

When

checking
the
level

of
com

pressor
oil
or

when

replacing
any

component
part
of
the

system
use
the

following
service

procedure
This

fa

cilitates
to
return
oil
to

compressor

I

Operate
compressor
at

engine

idling
speed
1
000

rpm
or

below

with
controls
set

for
maximum

cooling
Air

Conditionin
j

and

high
blower

speed
for
10
to

15

minutes
in

order
to
return

compressor

oil
to

compressor

2

Stop
the

engine
and

discharge

refrigerant
of

system
and
then

remove

compressor
from

the
vehicle

3
Remove

compressor
fIller

plug

Drain

compressor
oil
from

compres

sor
oil

sump
and

measure
the

amount

4

Compressor
oil
is

satisfactory
if

the

following
amount
of
oil

remains
in

the

compressor

Residual
oil

S5
to
128

gr
3
to
4
oz

5
Check
the
cleanliness
of
the
oil
If

the
oil
contains

chips
or

other

foreign

material
clean
oil

5ump
with
new

oil

6
Discard
the

used
oil
and

fili
with

the
same
amount
of
new
oil
Add

oil
if

found
less
than
above
amount

Fig
AC
27

Filler

plug

If

compressor
is

inoperative
due
to

faulty
compressor
or

heavy
loss
of

refrigerant
remove

compressor
and

repair
as

necessary
Then

pour
oil

up

to
correct
level
and
install
on

engine

After
above

steps
have
been

complet

ed
recheck
oil
level
drain
oil
to

correct
level
if

level
is

excessively
high

PERFORMANCE
TEST

The
cooling

performance
of
the
air

conditioner

changes
considerably
with

changes
in

surrounding
conditions

Testing
must
be

performed
using
the

correct
method
This

test
is
used
to

judge
whether

system
is

operating
cor

rectly
and

can
also
be
used

as
a

guide

in

checking
for

problems

I

Park
the
vehicle
indoors
or
in
the

shade

AC
17
2

Open
all
the
windows
of
the

vehicle
fully
However

close
the

doors

3

Open
the
hood

4

Connect
manifold

gauge
to

high

and
low
side
service
valves
of
the

system
Refer
to

Handling
Manifold

Ga

uge

5

Set
fan
control
lever
to
maxi

mum

6
Set

temperature
control
lever

to

max
cool

position

7
Start
the

engine
and
hold

engine

speed
at
1
500

rpm

S
After
the
air

conditioner
has
been

operated
for
about
10
minutes

measure

system

pressures
at

high
pres

sure

discharge
side
and
low

pressure

suction
side

9
Measure
the

temperature
of
dis

charge
air
at

outlet

grille

10
Measure
the

temperature
of

capin

11
Measure
ambient

temperature

and

humidity
one
meter
3
3
ft

away

from
condenser
front
Be

careful
not

to

expose
dry
buib

and
wet
bulb

to

direct

sunlight

12
Check
for

any
abnormalities

by

comparing
the
test

results
with
stand

ard

pressure
in
Performance

Chart

Notes

a
The

pressure
will

change
in
the

followi

g
manner
with

changes
in

conditions

When

blower

speed
is

low
dis

charge

pressure
will

drop

When
the
relative

humidity
of
in

take
air
is
low

discharge
pressure

will

drop

b

The

temperature
will

change
in
the

following
manner
with

changes
in

conditions

When
the
ambient
air

temperature

is

low
the
outlet
air

temperature

will
become
low

If
the
test
reveals
that
there
is

any

abnormality
in

system
pressure
isolate

the

cause
and

repair
by
reference
to

the
Trouble

Diagnoses
and
Cor

rections

Air

Conditioning

TROUBLE
DIAGNOSES
AND
CORRECTION

CONTENTS

COOLING
DIAGNOSES

FUNCTION
TEST

STANDARD
PERFORMANCE

PERFORMANCE

TEST
DIAGNOSES
AC19

AC
20

AC
20

AC21
COMPRESSOR

DIAGNOSES

NOISE

DIAGNOSES

BLOWER
MOTOR

DIAGNOSES
AC
22

AC23

AC24

COOLING
DIAGNOSES

INSUFFICIENT
COOLING

I

I

Check
amount
of

discharged
air

j

If
OK
No
or
insufficient

discharged
air

Performance
test

Refer
to

performance

test
on
the

following

page
1

ChecK
blower

I

I

I
If
OK

I

I

Repair
cooling

unit
Blower

stops
Check

sight
glass
for
bubbles

I

I

Many
bubbles

I

I
No
or

few
bubbles

Check
refrigeration
line

for

leakage

Note
If
there

are
too

many
bubbles

stop
compressor
and

check
for

leaks

Then

evacuate
and

recharge

system
Refer
to

Blower
motor

diagnoses

I

If

OK
lfleaks

Discharge
the

system

Evacuate

and

recharge
Repair
leaks
and

recharge

AC
19

Air

Conditioning

PERFORMANCE
TEST
DIAGNOSES

Condition

Discharge
air
too
warm

a
Both

discharge
and
suction

pres

sure
too

high

b
Both

discharge
and
suction

pres

sure
too
low

c
Discharge

pressure
too

high
and

suction

pressure
too
low

d
Suction

pressure
too

high
and

discharge

pressure
too
low

e

Discharge

pressure
normal
and

suction

pressure
too

high

t
Discharge

pressure
normal
and

luction

pressure
too
low

g
Suction

pressure
normal
and

discharge
pressure
too

high

h
Both

discharge
and
suction

pres

sure
normal

Air

conditioning
is

operating

properly

Discharge
air
normal

or
too
cold

a

Discharge
pressure
normal
and

suction

pressure
too
low
Probable
cause

Air

mixed
with
refrigerant
in

system

Overcharge
of

refrigerant

Loose
fan
belt
or

engine
over

heating

Obstructed
or

dirty
condenser
fins

Insufficient

refrigerant
charge

Over

filling
of

compressor
oil

Damaged
compressor
valve
or

pack

ing

Loose

compressor
drive
belt

Clutch

slippage

Faulty
expansion
valve

Clogged
expansion
valve
strainer

Water
has
frozen
at

expansion

valve

Faulty
expansion
valve

Faults
of
both

a
and
h
exist

Air
leaks
from

engine
com

partment

Restricted
air
flow

through
evapo

ratof

Slow
blower
motor

speed

AC
21
Corrective
action

Evacuate
and

charge
system

Discharge
some
of

refrigerant
to

correct
level

Adjust
fan
belt
or
check

cooling

system

Clean
exterior

surface
with
water

Add

refrigerant

Drain
oil
and
correct
oil
level

Refer

to

Compressor
oil
level

check

Repair
or

replace
compressor
Refer

to

Compressor

Adjust

Repair
Refer
to

Compressor

Reinstall

sensing
bulb
correctly
to

keep
it

tight
to

pipe

Replace

Clean
strainer

Evacuate
and

charge
system

Replace

Correct

sealing

Clean

evaporator
fins

Check
and

repair
blower
motor
and

wiring

Air

Conditioning

NOISE
DIAGNOSES

NOISY

I

I

I
Set
fan

switch
on

2

Change
the

engine
rpm

frequently

Detect

the
source
of

noise

I

From

engine
compartment
From
cabin

Cooling
unit

j

Check
the

resonant
sound
when
the

engine
rpm
is

changed

I

I

No

resonant
sound

Compressor
itself
makes
noise
j

Blower
motor

makes
noise

Replace
or

repair
blower

Resonant

sound

Repeat
compressor
clutch
ON
and

OFF

This

checking
can
be

performed
by
changing

engine
rpm
while

fan
switch
is

set
at

ON
Retighten
compressor
bracket
bolt

If

piping
is

resonating
add

clip

Noisy
only
when
clutch
is

engaged
Noisy
when

clutch
is
not

engaged

I

Check
drive
belt
for

slackness

Check
for
loose

compressor
mounting
bolts

I

I
Remove

compressor
belt
then
turn

compressor

pulley

by
hand
If
noise
is
heard

repair
com

pressor
clutch

If

OK

If
loose

Compressor
itself
makes
noise

Repair
or

replace
compressor
Retighten
or

adjust

Nl1

Air

Conditioning

BLOWER
MOTOR
DIAGNOSES

Blower
motor

inoperative

Check
fuse

In
fuse
block

15A
W

Single
fuse
15A
at

cooling
unit

I

j

If
OK

Check
the

continuity
and

fitting
of
fan
switch

I

I

If
OK

I

I

Connect
fan
switch
to

wiring
harness

2

Turn
the

ignition
switch
ON
IG

3
Set
fan
switch
at
ON
1
2
or
3

position

Check
the

voltage
for
blower
motor

Blue
lead
wire
is

poweI
source

Blue
wire

with
white

stripe
is

for

grounding

I

I
Voltage

I

I

Check
the

continuity
and

fitting
of
resistance
on

cooling
unit

I

I
If
OK
If

damaged

I
I

Replace
blower
motor
Replace
resistance

AC

24
mown
fuse

Replace
fuse

j

If

damaged

I

I

Replace
fan
switch

No

voltage

Replace
main
relay

Air

Conditioning

REMOVAL
AND
INSTALLATION

COMPRESSOR

REMOVAL

INSTALLATION

IDLER
PULLEY

FAN
BELT

TENSION
ADJUSTMENT

REMOVAL
AND
INSTALLATION

INSPECTION

COOLING
UNIT

REMOVAL
AND
INSTALLATION

DISASSEMBLY
AND
ASSEMBLY

INSPECTION

RECEIVER
DRYER
AND
PIPING

COMPRESSOR

REMOVAL

I
Remove

battery

2

Disconnect

compressor
lead
wire

at
connector

3
Loosen
idler

pulley
lock

nut
then

adjusting
bolt
Remove

compressor

drive
belt

from

compressor
pulley

AC477

Fig
AC
28

Removing
drive
belt

4

Discharge
system
Refer
to
Dis

charging
System
under
General
Service

section
CONTENTS

AC
25

AC25

AC26

AC
27

AC
27

AC27

AC
27

AC27

AC
27

AC
2B

AC
29

AC
29
REMOVAL

AND
INSTALLATION

INSPECTION

WIRING

HARNESS
AND

COMPONENTS

WIRING
DIAGRAM

MAINTENANCE

MAIN
RELAY

COMPRESSOR

RELAY

FAN
SWITCH

RESISTOR
FOR
FAN
SWITCH

THERMO
SWITCH

F
I

C
D
SOLENOID
VALVE
AC29

AC29

AC30

AC30

AC31

AC31

AC31

AC31

AC32

AC32

AC
32

5
Remove
flexible
hose

fixing
plate

and
disconnect
low
and

high
pressure

flexible
hoses
from

compressor

Notes

a
Use
two

wrenches
when
disconnect

ing
pipe

joints

b

Plug
flexible
hose
and

compressor

joint
openings
immediately
after

disconnection
to

prevent
entry
of

dust
moisture
laden
air
etc

Fig
AC
29

Disconnecting
ftexible

hoses

from
compressor

6
Remove

bolts

securing
fuel
tube

to

compressor
attachment

AC
25
Y
1

L

AC744

7
Remove
four
bolts

securing
com

pressor
to
its
bracket

Compressor
and

attachment

can
now
be
detached
as
an

assembly

Notes

a
There
are
a

total
of
four
bolts
two

on

upper
side
of
bracket
and
two

on
lower
side
of

compreSsor

Loosen

upper
bolts
and
remove

lower
bolts
When

removing
upper

bolts

securely
hold

compressor

with
one
hand

b
When

installing
temporarily
tighten

upper
bolts
then

tighten
lower

bolts

2

R

C7

c

L

PJJ

I

8

INSTALLATION

a
c
J

l
i
rp

To
install

compressor
reverse
the

order
of
removal
Observe
the

follow

ing
nhlJo
e
trorf
1001

vom
R

i
n3

Wheliqli
liiAniitg

fiil
l
in

pt
l

witlil
tiiel
sam
efuouiitITof

b11
1fasitlult

used

previously
v
d
rnl

2

Oil

capacity
new

compressor

O
910
1

owt
llllt
blj
f
H
w
s
013
5

rlT
s

0
111
boc

19
bB1rllo

bi2

qqll
no

e

l
bffik
kuanM
mpdi

x
of

Jli
oln

L
il
m
1IlffiiOrb

fler
ot
oldm

F
n

Cheo

f
undeF
r
n
al

1
aQ

r1tIU
Jt
t31
HClJI1
t
JIVU

i
rlUI

1o
ifm
ft
q
t

VI
31U
S
ltlod

bnM
UfO
l
W

kldf

CJiJi
ti

WIf
nl

L
llil
g

ncn
d

oressor

M
et

illpuntinl
botts
if

l9Wul
fb

i
l
fI
I
l

1Ttio
l

qqlJ

necessary
re

Ighten

I

d
210
Air

Conditioning

Tightening

torque

Flexible
hose
to

compressor

dl

t
kg
J
l

IQ

1

Tf
es

oriti
ra

Lbolts

IbP
fo
o15g

m
J

r
f6i
o
20
i
il

f

J

rt
I

r

aGket
engine

Dons
1
1

0

1
1
3
16

5

l11fd
1l

V

f

42
3
3U
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not

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e
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ready
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Wheniiinstallingccomptess
i
turn

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When

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ssor

apD
v

a
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JU
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t
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f
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jJ

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26
5

1

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2

Compressor

3

Compressor
bracket

4
AHernator

5
Idler

pulley
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AC745

Fig
AC
31

Removing
compressor

6
Evacuate

cooling
system
then
re

charge
with

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to

Evacuating
and

Charging
System
under

l
r

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efal

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ectioo

f
iI
t

7
F

Whenever
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r

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J

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st
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r
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o
s

9

r
h

v

a

For

compressor
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and

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refer

to

1
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Yt
j
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c
S
t
q

b

Cheok

refrigerant

leakage
if

neces

sary
correct

dO
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n

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l

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2