Valeo TM08, Service Manual

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4-Troubleshooting
A/C cycle diagnosis by gauge pressure
Following is a diagnosis procedure to connect gauge manifold to A/C cycle, measure suction and
discharge pressures and analyze the defects of the cycle.
Operation conditions of the A/C cycle for pressure mesuring:
1. Ambient temperature: 30 - 35 °C
2. Engine speed: 1,500 rpm
3. A/C switch: ON
4. Blower speed: high
5. Temperature control: full cold
Gauge pressure
indication
Cause Confirmation method Action to take
Pressure is normal A/C cycle operates normally.
If there is any defect (poor cooling performance), there shall be another
cause
Both discharge and
suction pressures are
low
Refrigerant shortage Connect gauge
manifold to cycle
Recover refrigerant,
then refill with the
right amount of
refrigerant
Receiver dryer is
clogged
Temperature difference
between inlet and
outlet pipes happens.
Dryer is covered with
frost
Replace parts
Expansion valve is
clogged
Expansion valve was
covered with frost
Clean or replace part
Enclosure leakage from
the Expansion valve’s
temperature sensing
tube.
(Expansion valve
operates to close the
valve opening)
Outlet side of the
expansion valve is not
cooling.
(Low side of gauge
indicates vacuum)
Replace part
Temperature sensing
device at outlet air is
defective
Evaporator becomes
frozen up
Adjust or replace the
part
Refrigerant piping is
clogged or crashed
If any part between
the dryer and the
compressor is clogged
or crashed, the low
side pressure becomes
vacuum
Adjust or replace the
part
Discharge pressure: around 0.9 - 1.6 MPaG (10 - 17 kgf/cm²)
Suction pressure: around 0.03 - 0.10 MPaG (1.3 - 2.0 kgf/cm²)
Suction pressure
becomes vacuum