1B-10
AIR CONDITIONING (OPTIONAL)
DETAIL DIAGNOSIS TABLE AT AMBIENT TEMPERATURE WITHIN 30 – 35
C (85 – 95
F)
MPa
MANIFOLD
kg/cm
2
GAUGE
psi
CONDITION
CAUSE
CORRECTION
Lo
Hi
0.2 – 0.3
2.0 – 3.0
28.4 – 42.6
1.18 – 1.47
12.0 – 15.0
170 – 213
Normal condition.
Negative
pressure
0.5 – 0.6
5 – 6
71.2 – 85.3
The low pressure side
reads a negative pressure,
and the high pressure side
reads an extremely low
pressure.
Presence of frost around
tubing to and from receiver/
dryer and expansion valve.
Dust particles or water
droplets are either stuck or
frozen inside expansion
valve, preventing the re-
frigerant from flowing.
Gas leak from heat-sensi-
tizing tube is preventing
refrigerant flow.
Clean expansion valve.
Replace it if it cannot be
cleaned.
Replace receiver/dryer.
Evacuate the A/C system
and recharge with fresh re-
frigerant.
If heat-sensitizing tube is
defective, replace expan-
sion valve.
Normal:
0.2 – 0.3
2.0 – 3.0
28.4 – 42.6
Abnormal:
Negative
pressure
Normal:
1.18 – 1.47
12.0 – 15.0
170 – 213
Abnormal:
0.69 – 0.98
7 – 10
99.4 – 142
During A/C operation, the
low pressure side some-
times indicates negative
pressure, and sometimes
normal pressure. Also
high pressure side reading
fluctuates between the ab-
normal and normal pres-
sure.
Expansion valve is frozen
due to moisture in the sys-
tem, and temporarily shuts
off the
refrigeration cycle.
Replace expansion valve.
Replace receiver/dryer.
Evacuate A/C system and
recharge with fresh
refrigerant.
0.05 – 0.1
0.5 – 1.0
7.1 – 14.2
0.69 – 0.98
7 – 10
100 – 142
Both low and high
pressure sides indicate
low readings.
Continuous air bubbles
are visible through sight
glass.
Output air is slightly cold.
Insufficient refrigerant in
system.
(Refrigerant leaking)
Using a gas leak detector,
check for leaks and repair
as necessary.
Recharge refrigerant to a
specified amount.
If the pressure reading is al-
most 0 when the
manifold gauges are
attached, check for any
leaks, repair them, and
evacuate the system.
0.4 – 0.6
4 – 6
56.9 – 85.3
Pressure on low pressure
side is high.
Pressure on high pressure
side is low.
Both pressure becoming
equal right after A/C is
turned OFF.
Internal leak in compres-
sor.
Inspect compressor and re-
pair or replace as
necessary.
0.25 – 0.3
2 5
3 0
1.96 – 2.45
20
25
High pressure reading on
both low and high
pressure sides.
Air bubbles are not visible
even when engine rpm is
lowered.
Overcharged A/C system.
Faulty condenser
cooling operation.
Faulty condenser fan op-
eration.
Adjust refrigerant to
specified amount.
Clean condenser.
Inspect and repair
condenser fan.
2.5 – 3.0
35.6 – 42.6
20 – 25
285 – 355
High pressure reading on
both low and high
pressure sides.
Low pressure side tubing
is not cold when touched.
Air bubbles are visible
through sight glass.
Presence of air in A/C sys-
tem.
(Improperly evacuated)
Replace receiver/dryer.
Inspect quantity of com-
pressor oil and presence of
contaminants in oil.
Evacuate system and
recharge with fresh
refrigerant.
0.3 – 0.4
3.0 – 4.0
42.7 – 56.8
1.86 – 1.96
19 – 20
271 – 284
High pressure reading on
both low and high
pressure sides.
Large amount of frost or
dew on the low pressure
side tubing.
Faulty expansion valve or
improper attachment of
heat-sensitizing tube.
Refrigerant flow is not regu-
lated properly.
Inspect if heat-sensitizing
tube is properly attached.
Replace expansion valve.
