Chrysler DODGE D150 1993 Service Manual page 1444

• HEATING AND AIR CONDITIONING
24 - 7
AIR CONDITIONING SYSTEM
SIGHT GLASS REFRIGERANT LEWEL TEST
The sight glass, which is an integral part of the fil­
ter-drier, is a refrigerant level indicator (Fig. 2). To
check the refrigerant level, clean the sight glass and
start the engine. Place t h e air conditioning controls
on A/C, the fan switch on high and the temperature
lever on cool. The room temperature should be at
least 21°C (70°F). After operating for a few minutes
in this manner, check the sight glass.
SIGHT GLASS
FILTER
DRIER
ASSEMBLY
9024-3
Fig. 2 Sight Glass
(1) If the sight glass is clear, the A/C clutch is en­
gaged, 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, t h e A/C clutch is en­
gaged and there is not significant temperature differ­
ence between compressor inlet and discharge lines;
the system is empty or nearly empty. Connect a
gauge to the compressor discharge port. If the gauge
reads less t h a n 172 kPag (25 psi), the suction tube
cycling switch has failed.
(3) If the sight glass is clear and the A/C clutch is
disengaged; the clutch is defective or, the clutch circuit
is open, or the system is out of refrigerant. Perform suc­
tion tube cycling switch test to determine condition.
(4) If the sight glass shows foam or bubbles, the
system could be low on charge. Occasional foam or
bubbles is normal when the room temperature is
above 43°C (110°F) or below 21°C (70°F).
Adjust the engine speed to 1,300 RPM. Block the
airflow through the condenser to increase the com­
pressor discharge pressure to 1 552-1 724 kPag (225-
250 psig). If sight glass still shows bubbles or foam,
system charge level is low.
The refrigerant system will not be low on charge un­
less there is a leak. Find and repair the leak. If the leak
can be repaired without discharging the system, the low
refrigerant charge level can be corrected as follows.
Maintaining the discharge pressure of 1 550-1 720 kPag
(225-250 psig), add refrigerant gas through compressor
suction line until foam is cleared from sight glass. Then
add 13 oz. (368 g) or 1 can of refrigerant.
HIGH PRESSURE RELIEF WALWE
The high pressure relief valve vents only a small
amount of refrigerant necessary to reduce system pres­
sure and then reseats itself. The majority of the refrig­
erant is conserved in the system. The valve is calibrated
to vent at a pressure of 3 100-3 790 kPag (450-550
psig). However, the fact that the valve vented refriger­
ant, does not mean the valve is defective.
ELECTRONIC TEMPERATURE CYCLING
SWITCH TEST
The electronic temperature cycling switch (Fig. 3) is
located on the refrigerant plumbing, suction line near
the H-valve. It electrically inputs to the engine control­
ler on gasoline vehicles and in series with the clutch
coil on diesel vehicles. The switch turns the compressor
on and off depending on the temperature in the suction
line. The switch is a sealed, specially calibrated unit
and if found defective, must be replaced.
ELECTRONIC
TEMPERATURE
CYCLING SWITCH
J 9 3 2 4 - 9 7
Fig. 3 Electronic Temperature Cycling Switch
(1) Remove the wires (boot connector) from the
electronic temperature cycling switch.
(2) Check continuity of the switch. Switch contacts
are closed at temperatures above 45°F (7°C). If no
continuity, replace switch.
(3) If contacts are closed, verify switch operation as
follows:
(a) Connect wires to cycling switch.
(b) Set temperature control lever to full cool position.
(c) Set A/C blower motor on low speed and push
A/C button.
(d) Operate engine at 1,300 RPM for approxi­
mately 5 minutes to stabilize the A/C system and
verify t h a t refrigerant system is full.