Isuzu Amigo / Axiom / Trooper / Rodeo / VehiCross. Manual — part 1079
1A–38 HEATING, VENTILATION AND AIR CONDITIONING (HVAC)
Checking The Refrigerant System With Manifold Gauge
Since Refrigerant-134a (HFC-134a) is used in the air
conditioning system in this vehicle, be sure to use
manifold gauges, charging hoses and other air
conditioning service tools for HFC-134a when
checking the refrigerant system.
Conditions:
D
Run the engine at idle
D
Air conditioning switch is “ON”
D
Run the blower motor at “HIGH” position
D
Temperature control lever set to “MAX COLD”
D
Air source selector lever at “CIRC”
D
Open the engine hood
D
Close all the doors
Normal Pressure:
D
At ambient temperature: approx. 25–30
°
C
(77–86
°
F).
D
At low-pressure side: approx. 147.1–294.2 kPa
(21.3–42.7 psi).
D
At high-pressure side: approx. 1372.9–1863.3 kPa
(199.1–270.2 psi).
Refer to the table on the refrigerant pressure-temperature
relationship.
HFC-134a Pressure-Temperature Relationship
Pressure
Temperature
(kPa)
(psi)
(
°
C)
(
°
F)
36
5.3
–20
–4.4
67
9.7
–15
5
104
15
–10
14
147
21
–5
23
196
28
0
32
255
37
5
41
314
45
10
50
392
57
15
59
471
68
20
68
569
82
25
77
677
98
30
86
785
114
35
95
912
132
40
104
1059
154
45
113
1216
176
50
122
HEATING, VENTILATION AND AIR CONDITIONING (HVAC) 1A–39
Connect The Manifold Gauge
Low-pressure hose (LOW) — Suction side
High pressure hose (HI) — Discharge side
901R100020
Legend
(1) Low Side
(2) High Side
1A–40 HEATING, VENTILATION AND AIR CONDITIONING (HVAC)
Condition
Possible cause
Correction
Discharge (High Gauge) Pressure
Abnormally High
Condenser clogged or dirty.
Clean the condenser fins
Abnormally High
Cooling fan does not operate
properly.
Check the cooling fan operation.
Discharge (High Gauge) Pressure
Abnormally High.
Insufficient cooling.
Excessive refrigerant in system.
Discharge and recover refrigerant.
Recharge to specified amount.
Discharge (High Gauge) Pressure
Abnormally High.
High pressure gauge drop. (After
stopping A/C, the pressure drops
approx. 196 kPa (28 psi) quickly)
Air in system.
Evacuate and charge refrigerant
system.
Discharge (High Gauge) Pressure
Abnormally Low.
Insufficient cooling
Insufficient refrigerant in system.
Check for leaks. Discharge and
recover the refrigerant. Recharge to
the specified amount.
Discharge (High Gauge) Pressure
Abnormally Low.
Low pressure gauge indicates
vacuum.
Clogged or defective expansion
valve.
Replace the expansion valve.
Discharge (High Gauge) Pressure
Abnormally Low.
Frost or dew on refrigerant line
before and after the receiver/drier or
expansion valve, and low pressure
gauge indicates vacuum.
Restriction caused by debris or
moisture in the receiver/drier.
Check system for restriction and
replace the receiver/drier.
Discharge (High Gauge) Pressure
Abnormally Low.
Compressor seal defective
Repair or replace the compressor.
High and low pressure gauge
balanced quickly. (After turned off
A/C)
Poor compression due to a defective
compressor gasket.
Repair or replace the compressor.
Suction (Low Gauge) Pressure
Abnormally High.
Low pressure gauge (Low pressure
gauge is lowered after condenser is
cooled by water.)
Excessive refrigerant in system.
Discharge and recover refrigerant
Recharge to specified amount.
Suction (Low Gauge) Pressure
Abnormally High.
Low pressure hose temperature.
(Low pressure hose temperature
around the compressor refrigerant
Unsatisfactory valve operation due
to defective temperature sensor of
expansion valve.
Replace the expansion valve.
around the com ressor refrigerant
line connector is lower than around
evaporator.)
Expansion valve opens too long.
Replace the expansion valve.
Suction (Low Gauge) Pressure
Abnormally High.
High and low pressure gauge
balanced quickly. (After turned off
A/C)
Compressor gasket is defective.
Repair or replace the compressor.
Suction (Low Gauge) Pressure
Abnormally Low.
Insufficient cooling.
Insufficient refrigerant in system.
Check for leaks. Discharge and
recover the refrigerant. Recharge to
specified amount.
Suction (Low Gauge) Pressure
Abnormally Low.
Frost on the expansion valve inlet
line
Expansion valve clogged.
Replace the expansion valve.
HEATING, VENTILATION AND AIR CONDITIONING (HVAC) 1A–41
Condition
Correction
Possible cause
Suction (Low Gauge) Pressure
Abnormally Low
Receiver/drier inlet and outlet
refrigerant line temperature. (A
distinct difference in temperature
develops.)
Receiver/Drier clogged.
Replace the receiver/drier.
Suction (Low Gauge) Pressure
Abnormally Low.
Expansion valve outlet refrigerant
line. (Not cold and low pressure
gauge indicates vacuum.)
Expansion valve temperature sensor
is defective.
Replace the expansion valve.
Suction (Low Gauge) Pressure
Abnormally Low.
When the refrigerant line is clogged
or blocked, the low pressure gauge
reading will decrease, or a vacuum
reading may be shown.
Clogged or blocked refrigerant line.
Replace refrigerant line.
Suction (Low Gauge) Pressure
Abnormally Low.
Evaporator core is frozen.
Thermo switch defective.
Replace thermo switch.
Suction (Low Gauge) and Discharge
(High Gauge) Pressure Abnormally
High.
Excessive refrigerant in system.
Discharge and recover the
refrigerant, the Recharge to the
specified amount.
Insufficient cooling.
Condenser clogged or dirty.
Clean the condenser fin.
Suction (Low Gauge) and Discharge
(High Gauge) Pressure Abnormally
High.
Suction (Low) pressure hose (Not
cold).
Air in system.
Evacuate and charge refrigerant.
Suction (Low Gauge) and Discharge
(High Gauge) Pressure Abnormally
Low.
Insufficient cooling
Insufficient refrigerant in system.
Check for leaks. Discharge and
recover refrigerant. Recharge to
specified amount.
A/C — Air Conditioning
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