Jeep XJ. Manual — part 511
(2) Connect and dispense 0.283 kilograms (0.625
pounds or 10 ounces) of R-134a refrigerant into the
evacuated refrigerant system. See Refrigerant Sys-
tem Charge in this group for the procedures.
(3) Position the vehicle in a wind-free work area.
This will aid in detecting small leaks.
(4) With the engine not running, use a electronic
R-134a leak detector and search for leaks. Because
R-134a refrigerant is heavier than air, the leak detec-
tor probe should be moved slowly along the bottom
side of all refrigerant lines, connector fittings and
components.
(5) To inspect the evaporator coil for leaks, insert
the electronic leak detector probe into the center
instrument panel outlet. Set the blower motor switch
to the lowest speed position, and the mode control
switch in the recirculation mode.
SYSTEM LOW
(1) Position the vehicle in a wind-free work area.
This will aid in detecting small leaks.
(2) Bring the refrigerant system up to operating
temperature and pressure. This is done by allowing
the engine to run with the air conditioning system
turned on for five minutes.
(3) With the engine not running, use a electronic
R-134a leak detector and search for leaks. Because
R-134a refrigerant is heavier than air, the leak detec-
tor probe should be moved slowly along the bottom
side of all refrigerant lines, connector fittings and
components.
(4) To inspect the evaporator coil for leaks, insert
the electronic leak detector probe into the center
instrument panel outlet. Set the blower motor switch
to the lowest speed position, and the mode control
switch in the recirculation mode.
VACUUM SYSTEM
Vacuum control is used to operate the mode doors
in the heater-only and heater-A/C housings. Testing
of the heater-only and heater-A/C mode control
switch operation will determine if the vacuum, elec-
trical, and mechanical controls are functioning. How-
ever, it is possible that a vacuum control system that
operates perfectly at engine idle (high engine vac-
uum) may not function properly at high engine
speeds or loads (low engine vacuum). This can be
caused by leaks in the vacuum system, or a faulty
vacuum check valve.
A vacuum system test will help to identify the
source of poor vacuum system performance or vac-
uum system leaks. Before starting this test, stop the
engine and make certain that the problem is not a
disconnected vacuum supply tube at the engine
intake manifold vacuum tap or at the vacuum reser-
voir.
Use an adjustable vacuum test set (Special Tool
C-3707-B) and a suitable vacuum pump to test the
heater-A/C vacuum control system. With a finger
placed over the end of the vacuum test hose probe
(Fig. 9), adjust the bleed valve on the test set gauge
to obtain a vacuum of exactly 27 kPa (8 in. Hg.).
Release and block the end of the probe several times
to verify that the vacuum reading returns to the
exact 27 kPa (8 in. Hg.) setting. Otherwise, a false
reading will be obtained during testing.
VACUUM CHECK VALVE
(1) Remove the vacuum check valve. The valve is
located in the vacuum supply tube (black) at the
heater-A/C system vacuum tee.
(2) Connect the test set vacuum supply hose to the
heater-A/C control side of the valve. When connected
to this side of the check valve, no vacuum should
pass and the test set gauge should return to the 27
kPa (8 in. Hg.) setting. If OK, go to Step 3. If not OK,
replace the faulty valve.
(3) Connect the test set vacuum supply hose to the
engine vacuum side of the valve. When connected to
this side of the check valve, vacuum should flow
through the valve without restriction. If not OK,
replace the faulty valve.
HEATER-A/C CONTROLS
(1) Connect the test set vacuum probe to the heat-
er-A/C vacuum supply (black) tube at the tee in the
engine compartment. Position the test set gauge so
that it can be viewed from the passenger compart-
ment.
Fig. 9 Adjust Vacuum Test Bleed Valve
1 – VACUUM PUMP TOOL C-4289
2 – VACUUM TEST SET C-3707
3 – BLEED VALVE
4 – PROBE
24 - 18
HEATING AND AIR CONDITIONING
XJ
DIAGNOSIS AND TESTING (Continued)
(2) Place the heater-A/C mode control switch knob
in each mode position, one position at a time, and
pause after each selection. The test set gauge should
return to the 27 kPa (8 in. Hg.) setting shortly after
each selection is made. If not OK, a component or
vacuum line in the vacuum circuit of the selected
mode has a leak. See the procedure in Locating Vac-
uum Leaks.
CAUTION: Do not use lubricant on the switch ports
or in the holes in the plug, as lubricant will ruin the
vacuum valve in the switch. A drop of clean water
in the connector plug holes will help the connector
slide onto the switch ports.
LOCATING VACUUM LEAKS
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS,
REFER
TO
GROUP
8M
-
PASSIVE
RESTRAINT SYSTEMS BEFORE ATTEMPTING ANY
STEERING
WHEEL,
STEERING
COLUMN,
OR
INSTRUMENT PANEL COMPONENT DIAGNOSIS OR
SERVICE. FAILURE TO TAKE THE PROPER PRE-
CAUTIONS COULD RESULT IN ACCIDENTAL AIR-
BAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.
(1) Disconnect
the
vacuum
harness
connector
behind the glove box and inboard of the glove box
opening on the heater-A/C housing.
(2) Connect the test set vacuum hose probe to each
port in the heater-A/C housing half of the vacuum
harness connector, one port at a time, and pause
after each connection (Fig. 10). The test set gauge
should return to the 27 kPa (8 in. Hg.) setting
shortly after each connection is made. If OK, replace
the faulty heater-A/C control. If not OK, go to Step 3.
(3) Determine the vacuum line color of the vacuum
circuit that is leaking. To determine the vacuum line
colors, refer to the Vacuum Circuits chart (Fig. 11) or
(Fig. 12).
(4) Disconnect and plug the vacuum line from the
component (fitting, actuator, valve, switch, or reser-
voir) on the other end of the leaking circuit. Instru-
ment panel disassembly or removal may be necessary
to gain access to some components. See the service
procedures in this group.
(5) Connect the test set hose or probe to the open
end of the leaking circuit. The test set gauge should
return to the 27 kPa (8 in. Hg.) setting shortly after
each connection is made. If OK, replace the faulty
disconnected component. If not OK, go to Step 6.
(6) To locate a leak in a vacuum line, leave one
end of the line plugged and connect the test set hose
or probe to the other end of the line. Run your fin-
gers slowly along the line while watching the test set
gauge. The vacuum reading will fluctuate when your
fingers contact the source of the leak. To repair the
vacuum line, cut out the leaking section of the line.
Then, insert the loose ends of the line into a suitable
length of 3 millimeter (0.125 inch) inside diameter
rubber hose.
SERVICE PROCEDURES
REFRIGERANT OIL LEVEL
When an air conditioning system is assembled at
the factory, all components except the compressor are
refrigerant oil free. After the refrigerant system has
been charged and operated, the refrigerant oil in the
compressor is dispersed throughout the refrigerant
system. The accumulator, evaporator, condenser, and
compressor will each retain a significant amount of
the needed refrigerant oil.
It is important to have the correct amount of oil in
the refrigerant system. This ensures proper lubrica-
tion of the compressor. Too little oil will result in
damage to the compressor. Too much oil will reduce
the cooling capacity of the air conditioning system.
It will not be necessary to check the oil level in the
compressor or to add oil, unless there has been an oil
loss. An oil loss may occur due to a rupture or leak
from a refrigerant line, a connector fitting, a compo-
nent, or a component seal. If a leak occurs, add 30
milliliters (1 fluid ounce) of refrigerant oil to the
refrigerant system after the repair has been made.
Refrigerant oil loss will be evident at the leak point
by the presence of a wet, shiny surface around the
leak.
Refrigerant oil must be added when a accumulator,
evaporator coil, or condenser are replaced. See the
Refrigerant Oil Capacities chart. When a compressor
Fig. 10 Vacuum Circuit Test
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HEATING AND AIR CONDITIONING
24 - 19
DIAGNOSIS AND TESTING (Continued)
VACUUM CIRCUIT LEGEND
I. D.
Function
Color
A
Not Used
N/A
B
Defrost
Actuator (Full
Position)
Yellow
C
Floor Actuator
Brown
D
Defrost
Actuator
(Mid-Position)
Blue
E
Vacuum Supply
(Reservoir)
Black
F
Panel Actuator
Red
G
Not Used
N/A
Fig. 11 Vacuum Circuits - Heater Only
24 - 20
HEATING AND AIR CONDITIONING
XJ
SERVICE PROCEDURES (Continued)
VACUUM CIRCUIT LEGEND
I. D.
Function
Color
A
Not Used
N/A
B
Defrost Actuator (Full Position)
Yellow
C
Floor Actuator
Brown
D
Defrost Actuator (Mid-Position)
Blue
E
Vacuum Supply (Reservoir)
Black
F
Panel Actuator
Red
G
Recirculation Actuator
Green
Fig. 12 Vacuum Circuits - Heater-A/C
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HEATING AND AIR CONDITIONING
24 - 21
SERVICE PROCEDURES (Continued)
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