1989-Mitsu-Factory Manual · AC system · страница 17 из 42 · Открыть оригинал PDF ↗
SIGHT GLASS REFRIGERANT LEVEL TEST
The sight glass is a refrigerant level indicator. To
check the refrigerant level, clean the sight glass
and start the vehicle engine. Push the air condition-
er button to operate the compressor, place the
blower switch to high and move the temperature
lever to extreme left.
After operating for a few minutes in this manner,
check the sight glass.
(1) If the sight glass is clear, the magnetic clutch is
engaged, the compressor discharge line is
warm and the compressor inlet line is cool: the
system has a full charge.
(2) If the sight glass is clear, the magnetic clutch is
engaged and there is no significant tempera-
ture difference between compressor inlet and
discharge lines; the system has lost some
refrigerant.
(3) If the sight glass is clear and the magnetic
clutch is disengaged; the clutch is faulty or, the
system is out of refrigerant. Perform dual-pres-
sure switch test to determine condition. Check
dual-pressure switch and clutch coil for electri-
cal continuity.
Adjust the engine speed to 1,500 rpm. Block the
airflow through the condenser to increase the
compressor discharge pressure to 1,422 to 1,520
kPa (206 to 220 psi). If sight glass still shows
bubbles or foam, system charge level is low.
The refrigerant system will not be low on charge
unless there is a leak. Find and repair the leak. If
the leak can be repaired without discharging the
system an oil level check is not necessary. Use the
procedure for correcting low refrigerant level found
in the Refrigerant System Service Procedure Sec-
tion.
FUSIBLE PLUG
When ambient temperature of the fusible plug
reaches 105°C (221°F). the fusible plug melts and
the refrigerant in the system is released.
Once the fusible plug is operated, it cannot be
used again.
So. it is necessan/ to install new one and charge
the refrigerant in the system.
(4) If the sight glass shows foam or bubbles, the
system could be low on charge. Occasional
foam or bubbles are normal when the ambient
temperature is above 43°C (110°F) or below
21°C (70°F).
DUAL PRESSURE SWITCH
The dual pressure switch, located on the liquid line, is wired in
series with the magnetic clutch. It cuts off the electrical
power supply to the clutch when refrigerant pressure drops
below the control point of the switch. Whenever the system is
inactivated by the dual pressure switch due to refrigerant loss,
the refrigerant oil may have been lost. Therefore, to prevent
damage to the compressor due to operation without sufficient
lubrication, the leak must be repaired and add compressor oil
[I5 cc (0.5 fl.oz.)] before final charge of the system. The
switch is a sealed, factory calibrated unit. No attempt should
be made to adjust or otherwise repair it.
If it is found to be faulty it must be replaced.
To Test the Dual Pressure Switch (Engine Off)
(1) Jump the wire leads.
(2) Press the air conditioner switch and blower switch on.
(3) Momentarily turn the ignition switch on (do not crank the
engine), listen for the compressor clutch engaging.
(4) If the clutch does not engage, the fin thermistor, engine
coolant temperature switch or fuse may be faulty.
(5) If clutch engages, connect the manifold gauge set and
read pressure. At pressure of 210 kPa (30 psi) or above,
switch must actuate the clutch.
If the pressure is below 210 kPa (30 psi), the refrigerant
system is low in charge. For corrective action refer to
refrigerant leak repair procedt Are.
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