Jeep Cherokee 2000 Service Manual - page 1477
VIBRATION
Possible causes of blower motor vibration include:
• Improper blower motor mounting
• Improper blower wheel mounting
• Blower wheel out of balance or bent
• Blower motor faulty.
NOISE
To verify that the blower is the source of the noise,
unplug the blower motor wire harness connector and
operate the heater-A/C system. If the noise goes
away, possible causes include:
• Foreign material in the heater-A/C housing
• Improper blower motor mounting
• Improper blower wheel mounting
• Blower motor faulty.
BLOWER MOTOR RELAY
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.
RELAY TEST
The blower motor relay (Fig. 7) is located in a wire
harness connector that is secured to the heater-A/C
housing behind the glove box on the passenger side
of the vehicle, next to the heater-A/C wire harness
connector in the passenger compartment. Remove the
relay from its connector to perform the following
tests:
(1) A relay in the de-energized position should
have continuity between terminals 87A and 30, and
no continuity between terminals 87 and 30. If OK, go
to Step 2. If not OK, replace the faulty relay.
(2) Resistance between terminals 85 and 86 (elec-
tromagnet) should be 75
6 5 ohms. If OK, go to Step
3. If not OK, replace the faulty relay.
(3) Connect a battery to terminals 85 and 86.
There should now be continuity between terminals
30 and 87, and no continuity between terminals 87A
and 30. If OK, see the Relay Circuit Test procedure
in this group. If not OK, replace the faulty relay.
RELAY CIRCUIT TEST
For circuit descriptions and diagrams, refer to
8W-42 - Air Conditioning/Heater in Group 8W - Wir-
ing Diagrams.
(1) The relay common feed terminal cavity (30) is
connected to fused battery feed directly from a fuse
in the Power Distribution Center (PDC), and should
be hot at all times. Check for battery voltage at the
connector cavity for relay terminal 30. If OK, go to
Step 2. If not OK, repair the open circuit to the PDC
fuse as required.
(2) The relay normally closed terminal cavity (87A)
is not used for this application. Go to Step 3.
(3) The relay normally open terminal cavity (87) is
connected to the blower motor. When the relay is
energized, terminal 87 is connected to terminal 30
and provides full battery current to the blower motor
feed circuit. There should be continuity between the
connector cavity for terminal 87 and the blower
motor relay output circuit cavity of the blower motor
wire harness connector at all times. If OK, go to Step
4. If not OK, repair the open circuit to the blower
motor as required.
(4) The coil battery terminal cavity (86) is con-
nected to the ignition switch. When the ignition
switch is placed in the On position, fused ignition
switch output is directed from a fuse in the junction
block to the relay electromagnetic coil to energize the
relay. There should be battery voltage at the connec-
tor cavity for relay terminal 86 with the ignition
switch in the On position. If OK, go to Step 5. If not
OK, repair the open circuit to the junction block fuse
as required.
(5) The coil ground terminal cavity (85) is con-
nected to ground. This terminal supplies the ground
for the relay electromagnet coil. There should be con-
tinuity between the connector cavity for relay termi-
TERMINAL LEGEND
NUMBER
IDENTIFICATION
30
COMMON FEED
85
COIL GROUND
86
COIL BATTERY
87
NORMALLY OPEN
87A
NORMALLY CLOSED
Fig. 7 Blower Motor Relay
XJ
HEATING AND AIR CONDITIONING
24 - 13
DIAGNOSIS AND TESTING (Continued)