Jeep Cherokee 2000 Service Manual - page 416
trim cover and horn switch must be replaced as a
unit.
OPERATION
When the center area of the driver side airbag trim
cover is depressed, the electrically conductive grids
on the facing surfaces of the horn switch membranes
contact each other, closing the switch circuit. The
completed horn switch circuit provides a ground for
the control coil side of the horn relay, which activates
the relay. When the horn switch is released, the
resistive tension of the convex membrane separates
the two electrically conductive grids and opens the
switch circuit.
DIAGNOSIS AND TESTING
HORN RELAY
The horn relay (Fig. 2) is located in the junction
block on the right cowl side inner panel below the
instrument panel in the passenger compartment. If a
problem is encountered with a continuously sounding
horn, it can usually be quickly resolved by removing
the horn relay from the junction block until further
diagnosis is completed. Refer to Junction Block in
the Contents of Group 8W - Wiring Diagrams for
horn relay identification and location. For complete
circuit diagrams, refer to Horn/Cigar Lighter in the
Contents of Group 8W - Wiring Diagrams.
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) Remove the horn relay from the junction block.
Refer to Horn Relay in the Removal and Installa-
tion section of this group for the procedures.
(2) 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 3. If not OK, replace the faulty relay.
(3) Resistance between terminals 85 and 86 (elec-
tromagnet) should be 75
6
5 ohms. If OK, go to Step
4. If not OK, replace the faulty relay.
(4) 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, perform the Relay Circuit Test that
follows. If not OK, replace the faulty relay.
RELAY CIRCUIT TEST
(1) The relay common feed terminal cavity (30) is
connected to battery voltage and should be hot at all
times. If OK, go to Step 2. If not OK, repair the open
circuit to the fuse in the junction block as required.
(2) The relay normally closed terminal (87A) is
connected to terminal 30 in the de-energized position,
but is not used for this application. Go to Step 3.
(3) The relay normally open terminal (87) is con-
nected to the common feed terminal (30) in the ener-
gized position. This terminal supplies battery voltage
to the horn(s). There should be continuity between
the cavity for relay terminal 87 and the horn relay
output circuit cavity of each horn wire harness con-
nector at all times. If OK, go to Step 4. If not OK,
repair the open circuit to the horn(s) as required.
(4) The coil battery terminal (86) is connected to
the electromagnet in the relay. It is connected to bat-
tery voltage and should be hot at all times. Check for
battery voltage at the cavity for relay terminal 86. If
OK, go to Step 5. If not OK, repair the open circuit to
the fuse in the junction block as required.
(5) The coil ground terminal (85) is connected to
the electromagnet in the relay. It is grounded
through the horn switch when the horn switch is
depressed. On vehicles equipped with the Remote
Keyless Entry (RKE) system, the horn relay coil
ground terminal can also be grounded by the RKE
receiver in response to certain inputs related to the
RKE system. Check for continuity to ground at the
cavity for relay terminal 85. There should be conti-
nuity with the horn switch depressed, and no conti-
nuity with the horn switch released. If not OK, refer
to Horn Switch in the Diagnosis and Testing section
of this group.
Fig. 2 Horn Relay
TERMINAL LEGEND
NUMBER
IDENTIFICATION
30
COMMON FEED
85
COIL GROUND
86
COIL BATTERY
87
NORMALLY OPEN
87A
NORMALLY CLOSED
XJ
HORN SYSTEMS
8G - 3
DESCRIPTION AND OPERATION (Continued)