DATSUN PICK-UP 1977 Service Manual

DISCHARGING
SYSTEM

The

pressurized
refrigerant
gas
Ul

side

system
must
be

discharged
to
a

pressure
approaching
atmospheric

pressure
prior
to

evacuating
refrigerant

inside

system
This

operation
should

be
made
to

permit
safe
re
oval
when

replacing
system
components

I

Close

high
and
low

pressure

valves
of
manifold

gauge
fully

2

Connect
two

charging
hoses
of

manifold

gauge
to

their

respective

service
valves

3

Open
both
manifold

gauge
valves

slightly
and

slowly
discharge
refriger

ant
from

system
See

Figure
AC
17

Note

Do
not
allow

refrigerant
to
rush

out
Otherwise

compressor
oil
will

be

discharged
along
with
re

frigerant

AC735

Fig
AC

17
Discharging

system

Caution
Protect

fingers
with
cloth

against
frostbite

by
refrigerant

when

connecting
the

charging
hose

to

the
service
valve

or

disconnecting

it
therefrom
Air

Conditioning

EVACUATING
SYSTEM

1
Connect

high
and
low

pressure

charging
hoses
of

manifold

gauge
to

their

respective
service

valves
of

sys

tern

and
d

ischarge

refrigerant
from

system
Refer
to

Discharge
System

2

When

refrigerant
has
been

dis

charged
to

a

pressure
approaching
at

mospheric
pressure
connect
center

charging
hose
to
a

vacuum

pump

3
Close
both
valves
of
manifold

gauge
fully
Then
start

vacuum

pump

4

Open
low

pressure
valve
and
suck

old

refrigerant
from

ystem
See

Figure
AC
18

S

When
low

pressure
gauge
reading

has

reached
to

approximately
500

mm

Hg
20
in

Hg
slowly
open
high

pressure
valve

See

Figure
AC
19

6
When

pressure
inside

system
has

dropped
to

710
mm

Hg
28
in

Hg

fully
close
both
of

valves
of
manifold

gauge
and

stop
vacuum

pump
Let

stand
it

for
5

to
10
minutes
in

this

state

and
confirm
that
the

reading

does
not
rise

Notes

a
The
low

pressure
gauge
reads
lower

by
2S

mm

Hg
I

in

Hg

per
a
300

m

1
000
ft
elevation
Perform

evacu

ation

according
to
the

following

table

Elevation

m
ft
Vacuum
of

system

mm

Hg
in

Hg

0

0

300

I
000

600
2
000

900
3

000
710
28

68S
27

660
26

635
25

Note
Values
show

readings
of
the

low

pressure
gauge

AC

12
b
The
rate
of
ascension
of
the
low

pressure
gauge
should
be
less
than

2S
mm
Hg
I

in

Hg
in
five

min

utes

If
the

pressure
rises
or
the

specified

negative

pressure
can
not
be
obtained

there
is
a

leak
in
the

system
In
this

case
immediately
charge

system
with

refrigerant
and

repair
the
leak
de

scribed
in
the

following

I
Confirm
that
both
valves
of

manifold

gauge
are

fully
closed
and

then
disconnect
center

charging
hose

from

vacuum

pump

2
Connect
center
hose
to
can

tap

in

place
of
vacuum

pump
Attach

refrigerant
can
to

can

tap
and

pass

refrigerant
to
manifold

gauge

3

Loosen
the
connection
of
center

fitting
of
manifold

gauge
to

purge
air

from

center
hose

4

Open
low

pressure
valve
of
mani

fold

gauge
and

charge
refrigerant
into

system
After
one
can
about
0
4

kg
I

Ib
of

refrigerant
has
been

charged

into

system
close
low

pressure
valve

5

Check
for

refrigerant
leakage

with
a
leak
detector

Repair
any
leak

ages
found
Refer
to

Checking
for

Leaks
and

Refrigerant
Leaks

6
Confirm
that
both
valves
of

manifold

gauge
are

fully
closed
and

then

change
center

charging
hose
from

can

tap
to
vacuum

pump

7

Open
high
and
low

pressure

valves
and

operate
vacuum

pump
to

suck

refrigerant
from

system
When

the

pressure
in

system
has

dropped
to

710

mm

Hg
28
in

Hg
fully
close

both
valves
of
manifold

gauge

7

The
above

operation
completes

evacuation
of

system
Next

charge

refrigerant
Refer
to

Charging
Refrig

erant

J

I

1
Air

Conditioning

J

lJ

R

J

g

j

ru

Fig
A
C
l8

Euacuating

system
First

step
AC736

Fig
AC

19

Euacuatingsystem
Second

step
AC737

CHARGING

REFRIGERANT

I
Install

manifold

gauge
to

system

Refer
to

Handling
Manifold

Gauge

Notes

a

Be
sure
to

purge
air
from
the

high

and
low

pressure
charging
hoses

b
If
air
is

mixed
with

refrigerant
gas

in

system
evacuation
of

system

should
be

performed
Refer
to

Evacuating
System

2

Attach
center

charging
hose
of

manifold

gauge
to

refrigerant
can

through
can

tap
Break
seal
of

refriger

ant
can
to

allow

refrigerant
to
enter

manifold

gauge
Loosen

charging
hose

at
the
center

fitting
of
manifold

gauge

and

purge
air

from
inside

charging

hose
Refer
to

Handling
Can

Tap

3

Open
high
and
low

pressure

valves
of
manifold

gauge
and

charge

refrigerant
into

system
See

Figure

AC
20

Notes

a

When

refrigerant
charging
speed
is
1

j

jJ

i

j

Fig
AC
20
Charging
refrigerant
AC738

slow
immerse

refrigerant
can
in

water
heated
to

a

temperature
of

about

400C

l040F
However

note
that
this
is

dangerous
when

water
is

hot
See

Figure
AC
21

Cautions

a

Under

any
circumstances
the

refrig

erant
can
must
not
be

warmed
in

water
heated
to
a

temperature
of

over
520C

l2S0F

b
A

blow
torch
or

stove
must
never

be
used
to
warm

up
the
can
R

121
Immerse
in
water

heated

to
about

400C

1040F

Note
that

hot

water
is

dangerous

AC252

Fit
AC

21
Heating

refrigerant

AC13

Air
Conditioning

b

When

charging
hquefied
refrigerant

into
the

system
lith
the
can
turned

upside
down
to
reduce

charging

time

charge
it

only
through
high

pressure
valve
but
not

through
low

pressure
3
h
e

After

completion
of

charging
the

compressor
should

always
be

turn

ed
Several
times

manually
See

Figure
AC
22

t

UL
Q

v1ifl
j

AC739

Fig
A
C
22

ClUJrging
refrigerant
First

step

4
If

refrigerant
charging

speed
slows

down

charge
it
while

Iunning
the

compressor
for
ease
of

charging
After

having
taken
the

steps
up
to

3
above

proceed
with

charging
in

the

following

order

I
Shut
off

high

pressure
valve
of

manifold

gauge
back
into

refrigerant
can
and
can

may
explode

2

Run
the

engine
at

idling
speeds

about
1
500

rpm

3
Set
the

temperature
control

lever
and
fan
switch

at
maximum

cool

and
maximum

speed
respectively

4

Charge
refrigerant
while
con

trolling
low

pressure
gauge
reading
at

2
8

kgfcm2
40

psi
or
less

by
turning

in
or

out
low

pressure
valve
of
mani

fold

gauge
See

Figure
AC
23
Caution
Never

charge
refrigerant

through
high

pressure
side
of

sys

tem
since
this
will
force

refrigerant

t

AC740

Fig
A
C
23

Charging

refrigerant
Second

step

AC
14
5
When

refrigerant
can
is

empty

fully
close

both
Ives
of
manifold

gauge
and

replace
refrigerant
can
with

a

new
one

Before

opening
manifold

gauge

valve
to

charge
refrigerant
from
new

can

be
sure
to

purge
air
from
inside

charging
hose

6

Charge
the

specified
amount

of

refrigerant
into

system
by
weighing

charged
refrigerant
with
scale

Over

charging
will

cause

discharge

pressure

to

rise

AC255

Measure
the

amount
of

charged

refrigerant
with
a
scale

Make
a

note
of
the

amount

charged

from

can

Fig
AC

24
Measuring
refrigerant

Refrigerant
capacity

Unit

kg
lb

Refrigerant
Minimum

Maximum

R
12

0

7
1
5
0
9
2

0

Note
The

presence
of
bubbles
in

sight
glass
of

receiver

dryer
is
an

unsuitable
method
of

checking
the

amount

of

refrigerant
charged
in

system
The
state
of
the
bubbles
in

sight
glass
should

only
be
used
for

checking
whether
the
amount
of

charged
refrigerant
is
small
or
not

The
amount
of

charged
refrigerant

can
be

correctly

judged
by
means

of

discharge
pressure
Refer
to
Re

frigerant
Level
Check

7
After
the

specified
amount
of

refrigerant
has

been

charged
into

sys

tem
close
manifold

gauge
valves
Then

detach

charging
hoses
from
service

valves
of

system
Be
sure
to
install

valve

cap
to

service
valve

8

Confirm
that
there
are

no
leaks
in

system
by

checking
with
a
leak
detec

tor

Refer
to

Checking
for
Leaks

Note

Conducting
a
performance
test

prior
to

removing
manifold

gauge
is

a

good
sen
ice

operation
Refer
to

Performance

Test

CHECKING
FOR

LEAKS

Conduct
a

leak
test
whenever
leak

age
of
refrigerant
is

suspected
and

when

conducting
service

operations

which
are

accompanied
by
disassembly

Dr

loosening
of

connection
fittings
Air

Conditioning

Refrigerant
is
a

colorless
odorless

gas
and

leakage
from

system
is
diffi

cult
to
detect

Accordingly
the
use

of

a

leak
detector
facilitates

check
for

leaks

Two
methods
of

checking
are

available
one

employs
a
halide

leak

detector
which
burns

propane
gas
or

butane

gas
and
the
other

is
an
electric

type
leak

detector

HALIDE
LEAK
DETECTOR

Since
the

propane
leak
detector
and

butane
leak
detector

are
the

same
in

respect
to
their

operation
this

section

describes
the

operation
of
the

propane

leak
detector

The

copper
screen
is
heated

by
the

burning
of

propane
Refrigerant
gas

decomposes
to

color
the
flame
when

it

contacts
the
heated
screen
The

gas
to

be
checked
is
drawn
into

the

sampling

tube

and
sent
out
to
the
burner
A

refrigerant
leak
can

clearly
be
detected

by
variations
in
the
color
of
the
flame

Propane
type

NO
LEAK

SMALL

LEAK

LARGE
LEAK
Greenish

blue

Yellow

Purple
AC010
1

Copper
reaction

plate

2

Flame

adjusting
lines

3

Burner

4

Sampling
tube

5

Strainer

6

Gas
bomb

7
Flame

adjuster

Fig
A
C
25

Checking
for
leak

Butane

type

Pale
blue

Bright
blue

Vivid

green

AC
15
I

Discharge

refrigerant
in

one
or

two
seconds
to
ascertain

that

system

has
a

sufficient

pressure
needed
for

leak
detection

Charge
with
04

kg
I

lb
of

refrigerant
if

necessary

2

Light
leak
detector

Adjust
the

height
of

the
ilame
between

flame

adjusting
lines
at
the

top
and
bottom

of
combustion

tube
A

reaction

plate

will

immediately
become
red

hot

3

Place
the
end

of

sampling
tube

near
the

point
of
the

suspected
leak

in

system

Notes

a
Since

refrigerant
gas
is
heavier
than

air

small
leaks
can
b

easily
detect

ed

by

placing
sampling
tube
direct

ly
below
the
check

point

b
Suitable
ventilation
is

required
If

refrigerant

gas
is

mixed
with
the

surrounding
air
leak
detector
will

always
indicate
a

response
and

detection
of
the
actual
leak
will
be

difficult

c

Never
bold
leak
detector
at
an

angle

Cautions

a
Never

inhale
the
fumes

produced

by
combustion
of

refrigerant
gas

since

they
are
toxic

b
Never
use
halide
torch
in
a

place

where
combustible
or

explosive

gas

is

present

4
The

ilame
will
be
almost

colorless

when
there
is

no

refrigerant
gas
being

burned
When
there
is

a
small

refriger

ant

gas
leak
the
ilame

will
be

green
or

yellowgreen
When

refrigerant

gas
leak

age
is

large
the
ilame
will
be
brilliant

blue
or

purple
Since
the
color
of
the

ilame
will
be

yellow
when
dust
is

being
burned
Or
there
is

aging
scale
on

copper
reaction

plate
always
keep
the

strainer
of

sampling
tube
and
reaction

plate
clean

5

Major
check

points

I
Compressor

Compressor
shaft
seal

rotate
the

compressor
by
hand

Oil
filler

plug

Flexible
hose
connections

Rear
cover
and
side
cover

gaskets

Service
valve

2
Condenser

Condenser

pipe
fitting

Condenser
inlet
and
outlet

pipe

connections

I

3

Piping

Flared
section
of

high
pressure
and

low

pressure
flexible

hose

Pipe
connections

rvice

valve

4

Evaporator
housing

Jnlet
and

outlet

pipe
connections

Expansionvalve

ELECTRIC
LEAK
DETECTOR

for
the

operational
procedures

refer
to

the
instructions
furnished
with

each
electric
leak
detector

Amount

of

refrigerant
Air

Conditioning

REFRIGERANT

LEVEL
CHECK

SIGHT
GLASS

Sight
glass
is

provided
at
the

top
of

receiver

dryer
One

guide
for
whether

there
is

enough
refrigerant
in

system
is

given
by
observing

refrigerant
flow

through
sight
glass
However
this

method

is
unsuitable
for

judging
the

amount
of

refrigerant
The
correct

refrigerant
level

can
be

judged
by

measuring
t
e

system
pressures
in
ac

cordance
with
the

procedures
de

scribed
Performance
Test

I

Start
the

engine
and
hold

engine

speed
at
1
500

rpm

Almost
no

reftigerant

Check
item

Temperature
of

high
pressure

and
low

pressure
pipes
Almost
no
difference

between

high

pressure

and
low

pressure
side

temperature

Bubbles
flow
continu

ousty
Bubbles
will

disappeu
a
nd
some

thing
like
mist

will

now
when

rerrigeran

is

nearly
gone
State
insightglass

A

I
I

AC256

Pressure
of

system
High
pressure
side

is

abnormally
loW

Repa
ir
Stop

compressor
and

conduct
an
overall

check
Insufficient

High
pressure
side
is

warOl
and

low

pressure

side

is

fairly
cold

The
bubbles
are
seen

at
intervals
of
1
2

seconds

A

r

I

AC257

Both

pressures
on

high

and
low

preS
ure
sides

are

slightly
low

Check
for

gas
leakage

repair
as

required
re

plenish
and

charge

system

AC

16
2

Set

temperature
control
lever
to

maximum

position

3

Set
blower
to
maximum

speed

4

Check

sight
gla
after
the

lapse

of
about
five

minutes
Judge
according

to
the

following
table

AC741

Fig
AC
26

Temperature
control
lever

Suitable
Too
much

refri
crant

High
pressure
side
is

hot
and
low

pressure

side
is
cold
High

pressure
side
is

abnormally
hot

Almost

transparent

Bubbles

may
appear

when

engine

speed
is

raised
and
lowered
No
bubbles
can
be

seen

No
clear
difference
exists
between
these
two

conditions

M

II
I

AC258

Both

pressures
on

high

and
low

pressure
sides

are
normal
Both

pressures
on

high

and
low

pressure
sides

are

abnormally
high

Discharge
reft

gerant

from

service
valve
of

10
11

pressure
side

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

REFRIGERANT

LEAKS

If
leaks
are

noticeable

leaky
parts

should

be

repaired
Then

system

should
be

filled
with

refrigerant
Do

not

operate
compressor
with

refriger

ant

level
e

cessively
low

If
this
caution
is

neglected
a
burnt

compressor
will

result
since

heavy
loss

of

refrigerant
usually
indicates

heavy

loss
of

compressor
oil

If

system
has

been

exposed
to

atmosphere
for
an

extended

period
of
Air

Condition

ing

time

receiver

dryer
must

be

replaced

If
leaks
are

slight
and
no
air
is

present

in

system
add

refrigerant
as

necessary

To

detect
leaks
refer
to

relative

topics
under

Checking
for

Leaks

Here
is

how
leaks
are

stopped

I

Check

torque
on
the

connection

fitting
and

if
too
loose

tighten
to

the

proper

torque
Check
for

gas

leakage

with

a
leak

detector

2
If

leakage
continues

even
after

AC
18
the

fitting
has
been

retightened
dis

charge

refrigerant
from

system
discon

nect
the

fittings
and
check
its

seating

face
for

damage
Always

replace
even

if

damage
is

slight

3
Check

compressor
oil

and
add
oil

if

required

4

Charge

refrigerant
and
recheck

for

gas
leaks
If
no
leaks

are
found

evacuate

and

charge

system

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

FUNCTION
TEST

STANDARD
PERFORMANCE

The
air
conditioner
on
the

model

620

has
the
below

performance
char

acteristics
when
all
systems
are
in

good

condition

Compressor
pressure
is

also

indicated
below

N

E
24

j
23

22

21

20

19

18

17

16

15

14

13

I

12

u

0

6
0

5
0

4

0

3
0

2
0

1
0

20
25
30
35
40
45

Temperature
of
outside
air

ENGINE

FAN

TEMP
1

500

rpm

MAX

Fun
Cotd

20
15
10
5
0

Oc

Temperature
of

dischuge
air
Air

Conditioning

TEMPERATURE

Intake
In
the
cabin

Discharged
air
Pressure

160C
61
OF
30C
37OF
12

kg
cm2
170

psi

ISoC

64OF
50C
4IOF
13

kg
cm2

185
psi

220C
72OF
70C
45OF
15

kg
cm2
213

psi

270C

SIOF
100C
SOOF
IS

kg
cm2
256

psi

Note

Engine

FAN

TEMP
1

500

rpm

3

position

Cold
Max

REFRIGERANT
PRESSURE

Temperature
outside
Pressure

discharge
0

a

250C
77OF
18

kg
cm2

256

psi

Oc

35

300C
S6OF
15

kg
cm2
213

psi
u

Co

S

13

kg
cm2
IS5

psi
30

350C
95OF

25
400C
J05OF
J2

kg
cm2
170

psi
Pressure
suction

1
0

kg
cm2

14
psi

1
2

kg
cm2
17

psi

1
4

kg
cm2
20

psi

1

6

kg
cm2
21

psi

20

IS

AC
20

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