AIR CONDITIONING (OPTIONAL) 1B-13
Detail diagnosis table (at ambient temperature within 30 - 35 °C (85 - 95 °F))
Condition Possible Cause Correction
MANIFOLD
GAUGE
MPa
(kg/cm
2
)
(psi)
Detail
Lo Hi
0.23 - 0.35
(2.3 - 3.5)
(33 - 50)
1.4 - 1.75
(14 - 17.5)
(200 - 249)
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 drop-
lets are either stuck or frozen
inside expansion valve, pre-
venting the refrigerant from
flowing.
Clean expansion valve.
Replace it if it cannot be
cleaned.
Replace condenser/dryer.
Evacuate the A/C system and
recharge with fresh refriger-
ant.
Normal :
0.23 - 0.35
(2.3 - 3.5)
(33 - 50)
↑ ↓
↑ ↓↑ ↓
↑ ↓
Abnormal :
Negative
pressure
Normal :
1.4 - 1.75
(14 - 17.5)
(200 - 249)
↑ ↓
↑ ↓↑ ↓
↑ ↓
Abnormal :
0.7 - 1.0
(7 - 10)
(100 - 142)
During A/C operation, the
low pressure side some-
times indicates negative
pressure, and sometimes
normal pressure. Also high
pressure side reading fluc-
tuates between the abnor-
mal and normal pressure.
Expansion valve is frozen due
to moisture in the system, and
temporarily shuts off the
refrigeration cycle.
Replace expansion valve.
Replace condenser/dryer.
Evacuate A/C system and
recharge with fresh refriger-
ant.
0.05 - 0.15
(0.5 - 1.5)
(4.2 - 21.3)
0.7 - 1.0
(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 sys-
tem. (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
almost 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 compressor Inspect compressor and
repair or replace as neces-
sary.
0.35 - 0.45
(3.5 - 4.5)
(50 - 64)
2.0 - 2.5
(20 - 25)
(285 - 355)
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 opera-
tion.
Adjust refrigerant to specified
amount.
Clean condenser.
Inspect and repair condenser
fan.
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 condenser dryer.
Inspect quantity of compres-
sor oil and presence of con-
taminants in oil.
Evacuate system and
recharge with fresh refriger-
ant.
0.45 - 0.55
(4.5 - 5.5)
(64 - 78)
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.
Refrigerant flow is not regu-
lated properly.
Replace expansion valve.
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