Refrigerant System Tests
Use the following procedure to evaluate the perfor-
mance of the air conditioning system. If the system
does not operate within the following guidelines, fur-
ther diagnosis and repair may be necessary. The
dash outlet temperature will fluctuate during each
clutch cycle, and the temperature reading should be
taken at the lowest value.
1.
Park the vehicle out of direct sunlight, shut down
the engine, and chock the tires.
2.
Open the hood and leave the hood open for the
entire test.
3.
Open the driver and passenger doors and leave
the doors open for the entire test.
4.
Note the current ambient air temperature.
NOTE: High relative humidity reduces cooling
and could increase the dash outlet temperatu-
res, and high-side system pressures.
5.
Using the ambient air temperature readings
noted in the previous step, find the temperature/
pressure specifications in
that best
match your ambient conditions.
6.
Connect the test gauges to the high and low side
service ports.
7.
Place a thermometer in the center dash outlet. If
the vehicle is a SleeperCab, place another ther-
mometer in the lower sleeper outlet.
NOTE: EPA10 and owner-set idle limits may
prevent the warm-up run from continuing without
occasional throttle inputs.
8.
Start the engine and run the A/C for 15 minutes.
9.
Set the engine speed to 1500 rpm and engage
the engine fan.
10. Set the cab climate control panel to the following
settings:
•
air selection switch to face mode
•
air conditioning on
•
blower speed switch to high
•
temperature control switch to full cold
•
recirculation switch off
11. On SleeperCabs, set the sleeper climate control
panel to the following settings (or initiate "bunk
override" mode):
•
blower speed switch to high
•
temperature control switch to full cold
12. Allow the system to stabilize at least five minutes
or until the dash and sleeper outlet temperatures
have reached a minimum, then compare the sys-
tem values to the information in
. The
results should be close to those listed, but minor
discrepancies are not a guarantee that the sys-
tem has a refrigerant system problem.
Possible causes of refrigerant system com-
plaints:
•
Too much oil - High high-side pressure,
poor heat rejection at the condenser
•
Too much refrigerant - High high-side pres-
sure, good cooling
Approximate Temperature/Pressure Specifications at Moderate Humidity (less than 50%)
Ambient Air Temp.
Center Dash
Outlet Temp.
Service Port Pressures
A/C
Compressor
Status
A/C Compressor
Status
Comments
High Side
psi (kPa)
Low Side
psi (kPa)
65–75°F (18–24°C)
44–50°F (7–10°C)
94–124 (648–855)
18–25 (124–172)
approximately
50% duty cycle
Cycling on
evaporator freeze
protection
75–85°F (24–29°C)
45–60°F (7–16°C)
114–125 (786–862)
20–26 (138–179)
approximately
75% duty cycle
85–95°F (29–35°C)
55–70°F (13–21°C)
135–170 (931–1172)
23–28 (158–193)
On
On steady
95–105°F (35–41°C)
65–80°F (18–27°C)
160–200 (1003–1379)
25–30 (172–207)
On
On steady
Table 1, Approximate Temperature/Pressure Specifications at Moderate Humidity (less than 50%)
Heater and Air Conditioner Troubleshooting
83.00
Refrigerant System Tests
122SD and Coronado Workshop Manual, Supplement 9, June 2014
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