Jeep Cherokee 2000, Service Manual

Page: 1481 / 1528

If the floor outlet air temperature is too low, refer
to Group 7 - Cooling System to check the engine cool-
ant temperature specifications. Both of the heater
hoses should be hot to the touch. The coolant return
heater hose should be slightly cooler than the coolant
supply heater hose. If the return hose is much cooler
than the supply hose, locate and repair the engine
coolant flow obstruction in the cooling system. Refer
to Group 7 - Cooling System for the procedures.
OBSTRUCTED COOLANT FLOW Possible loca-
tions or causes of obstructed coolant flow:
•
Pinched or kinked heater hoses.
•
Improper heater hose routing.
•
Plugged heater hoses or supply and return ports
at the cooling system connections.
•
A plugged heater core.
If proper coolant flow through the cooling system is
verified, and heater outlet air temperature is still
low, a mechanical problem may exist.
MECHANICAL PROBLEMS Possible locations or
causes of insufficient heat:
•
An obstructed cowl air intake.
•
Obstructed heater system outlets.
•
A blend-air door not functioning properly.
TEMPERATURE CONTROL
If the heater outlet air temperature cannot be
adjusted with the temperature control knob on the
heater-A/C control panel, the following could require
service:
•
The heater-A/C control.
•
The temperature control motor.
•
The blend-air door.
•
Improper engine coolant temperature.
LOW PRESSURE CYCLING CLUTCH SWITCH
Before performing diagnosis of the low pressure
cycling clutch switch, be certain that the switch is
properly installed on the accumulator fitting. If the
switch is too loose it may not open the Schrader-type
valve in the accumulator fitting, which will prevent
the switch from correctly monitoring the refrigerant
system pressure. Remember that lower ambient tem-
peratures, below about -1° C (30° F), during cold
weather will open the switch contacts and prevent
compressor operation due to the pressure/tempera-
ture relationship of the refrigerant.
Also verify that the refrigerant system has the cor-
rect refrigerant charge. See Refrigerant System
Charge in the Service Procedures section of this
group for more information.
For circuit descriptions and diagrams, refer to
8W-42 - Air Conditioning/Heater in Group 8W - Wir-
ing Diagrams.
(1) Disconnect and isolate the battery negative
cable.
(2) Unplug the low pressure cycling clutch switch
wire harness connector from the switch on the accu-
mulator fitting.
(3) Install a jumper wire between the two cavities
of the low pressure cycling clutch switch wire har-
ness connector.
(4) Connect a manifold gauge set to the refrigerant
system service ports. See Refrigerant System Service
Equipment and Refrigerant System Service Ports in
the Description and Operation section of this group
for more information.
(5) Connect the battery negative cable.
(6) Place the heater-A/C mode control switch knob
in any A/C position and start the engine.
(7) Check for continuity between the two terminals
of the low pressure cycling clutch switch. There
should be continuity with a suction pressure reading
of 262 kPa (38 psi) or above, and no continuity with a
suction pressure reading of 141 kPa (20.5 psi) or
below. If OK, test and repair the A/C switch sense
circuit as required. If not OK, replace the faulty
switch.
REFRIGERANT SYSTEM LEAKS
WARNING: REVIEW THE WARNINGS AND CAU-
TIONS IN THE FRONT OF THIS GROUP BEFORE
LEAK TESTING THE SYSTEM.
If the air conditioning system is not cooling prop-
erly, determine if the refrigerant system is fully-
charged. See A/C Performance in this group for the
procedures. If the refrigerant system is low or empty;
a leak at a refrigerant line, connector fitting, compo-
nent, or component seal is likely.
An electronic leak detector designed for R-134a
refrigerant, or a fluorescent R-134a leak detection
dye and a black light are recommended for locating
and confirming refrigerant system leaks. Refer to the
operating instructions supplied by the equipment
manufacturer for proper care and use of this equip-
ment.
An oily residue on or near refrigerant system lines,
connector fittings, components, or component seals
can indicate the general location of a possible refrig-
erant leak. However, the exact leak location should
be confirmed with an electronic leak detector prior to
component repair or replacement.
To detect a leak in the refrigerant system with an
electronic leak detector, perform one of the following
procedures:
SYSTEM EMPTY
(1) Evacuate the refrigerant system. See Refriger-
ant System Evacuate in this group for the proce-
dures.
XJ
HEATING AND AIR CONDITIONING 24 - 17
DIAGNOSIS AND TESTING (Continued)