Isuzu Amigo / Axiom / Trooper / Rodeo / VehiCross. Service manual — part 14
HEATING, VENTILATION AND AIR CONDITIONING (HVAC) 1A–27
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.
1A–28 HEATING, VENTILATION AND AIR CONDITIONING (HVAC)
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
HEATING, VENTILATION AND AIR CONDITIONING (HVAC) 1A–29
Condenser Fan Diagnosis
While the air conditioning is ON, the cycling switch in the
triple pressure switch senses the refrigerant pressure,
and activates the condenser fan to improve the cooling
capacity of the condenser when the refrigerant pressure
exceeds a set pressure value. The condenser fan stops
when the air conditioning is turned “OFF” or when the
pressure goes down below the set pressure value.
D08R200041
Condition
Possible cause
Correction
Condenser fan does not run.
–
Refer to “Chart A”.
–
Refer to “Chart B”.
1A–30 HEATING, VENTILATION AND AIR CONDITIONING (HVAC)
Chart “A” Condenser Fan Does Not Run
Step
Action
Yes
No
1
Are 30A fuse normal?
Go to
Step 2
Replace
2
Is relay (X-16) normal?
Go to
Step 3
Replace
3
Is pressure switch normal?
Go to
Step 4
Switch defective
or insufficient
refrigerant.
4
Is fan motor normal?
Go to
Step 5
Replace
5
1. Disconnect condenser fan relay (X-16).
2. Check to see if battery voltage is present at the chassis side
relay terminal NO. X16-5.
Is there a battery voltage?
Go to
Step 6
Repair open
circuit between
Condenser Fan
fuse (30A) and
No.X16-5.
6
1. Reconnect condenser fan relay (X-16).
2. Check to see if battery voltage is present at chassis side
connector terminal No.C21-3.
Is there a battery voltage?
Go to
Step 7
Repair open
circuit between
fuse (10A) and
C21-3.
7
Check to see if continuity between chassis side relay terminal
No.X16-2 and the chassis side connector terminal No.C21-4.
Is there a continuity?
Go to
Step 8
Repair open
circuit.
8
Check to see if continuity between chassis side connector
terminal No. C16-1 and chassis side relay terminal No.X16-1.
Is there a continuity?
Poor ground or
open circuit
between chassis
side connector
terminal
No.X16-4 (or
No.C16-2) and
body ground
(No.C10).
Repair open
circuit.
Chart “B” Condenser Fan Does Not Stop
Step
Action
Yes
No
1
1. Disconnect the triple pressure connector.
Does condenser fan stop?
Replace the triple
pressure switch.
Replace the
condenser fan
relay.
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