1993 Jeep Cherokee

1993 ACCESSORIES & EQUIPMENT Chrysler Corp. Rear Window Defoggers

Jeep; Cherokee, Grand Cherokee, Grand Wagoneer, Wrangler

DESCRIPTION & OPERATION

System consists of 2 vertical bus bars and horizontal rows of heating elements fused to inside of rear glass. On Cherokee, power circuit to grid is protected by fuse No. 18 (25-amp) located in fuse box. Power for relay is protected by fuse No. 8 (20-amp) located in fuse box.

On Grand Cherokee and Grand Wagoneer, power circuit to grid is protected by circuit breaker No. 28 (30-amp) located in fuse box. Power for relay is protected by fuse No. 19 (15-amp) located in fuse box. Fuse No. 23, located in fuse box, controls power to switch light and side mirrors.

On Wrangler, power circuit to grid is protected by fuse No. 6 (25-amp) located in fuse box. Power for relay is protected by fuse No. 9 (15-amp) located in fuse box.

TESTING

NOTE: For terminal identification, see appropriate chassis wiring in WIRING DIAGRAMS.

SYSTEM TESTING

  1. On Wrangler, check fuses No. 6 and 9. On Cherokee, check
    HTD/WDW and TURN fuses. On Grand Cherokee and Grand Wagoneer, check
    fuses No. 19 and 23 and circuit breaker No. 28. Replace as necessary.

  2. If fuses are okay, check for voltage on battery side of
    fuse No. 6 (Wrangler), HTD/WDW fuse (Cherokee) or fuse No. 28 (Grand
    Cherokee and Grand Wagoneer). If battery voltage is not present,
    replace maxi-fuse in Power Distribution Center (PDC) located near
    coolant reservoir (Cherokee) or near battery (Wrangler, Grand Cherokee
    and Grand Wagoneer).

  3. If battery voltage is present, check ignition side of fuse
    No. 9 (Wrangler), TURN fuse (Cherokee) or fuse No. 19 (Grand Cherokee
    and Grand Wagoneer) for voltage. If battery voltage is not present,
    check for an open circuit from ignition switch.

DEFOGGER SWITCH TEST

Cherokee & Wrangler

  1. Disconnect defogger switch connector. Turn ignition switch
    to RUN position. Measure voltage at defogger switch connector terminal
    "D". About 5 volts should be present. If about 5 volts are not
    present, repair open circuit from relay.

  2. Measure resistance across switch terminals "B" and "D".
    See Figs. 1 and 2. With switch button depressed, approximately zero
    ohms should be present. Measure resistance across switch terminals "D"
    and "C". With switch button depressed, zero ohms should be present.
    Measure resistance across switch terminals "B" and "C". Approximately
    zero ohms should be present.

Grand Cherokee And Grand Wagoneer

1) Disconnect defogger switch connector. Using a jumper wire,

apply 12 volts to switch terminal No. 1. Using another jumper wire, connect terminal No. 3 of switch to ground. If switch indicator lights, go to next step. If indicator does not light, replace switch.

2) Remove jumper wires. Connect an ohmmeter between switch terminals No. 2 and 3. Depress switch. Ohmmeter should indicate 10 ohms. If ohmmeter does not indicate 10 ohms, replace switch. If ohmmeter indicates 10 ohms, check for an open circuit between terminal No. 1 and fuse No. 23, between terminal No. 3 and ground and between relay terminals No. 2 and 3.



92A22327

Fig. 1: Defogger Switch Terminal ID (Cherokee & Wrangler) Courtesy of Chrysler Motors.

Fig. 2: Defogger Switch Internal Component ID (Cherokee & Wrangler) Courtesy of Chrysler Motors.

DEFOGGER RELAY TEST

1) Disconnect defogger relay connector. Turn ignition switch
to RUN position. Measure voltage at relay connector terminal No. 4

(Cherokee and Wrangler) or No. 5 (Grand Cherokee and Grand Wagoneer). Battery voltage should be present. If battery voltage is not present, repair open circuit to fuse No. 9 (Wrangler), fuse No. 19 (Grand Cherokee and Grand Wagoneer) or HTD/WDW fuse (Cherokee).

  1. Measure voltage at relay connector terminal No. 4. Battery
    voltage should be present. If battery voltage is not present, repair
    open circuit from fuse No. 6 (Wrangler), TURN fuse (Cherokee) or
    circuit breaker No. 28 (Grand Cherokee and Grand Wagoneer).

  2. Turn ignition switch to OFF position. Check resistance
    between relay connector terminal No. 1 and left (drivers side) of
    defogger grid. Zero ohms should be present. If zero ohms are not
    present, repair open circuit between relay connector and left side of
    defogger grid.

  3. Measure resistance between relay connector terminal No. 2
    and ground. Zero ohms should be present. If zero ohms are not present,
    repair open circuit between relay connector and ground.

  4. Reconnect relay connector. Turn ignition switch to RUN
    position. Measure voltage at terminal No. 3. About 5 volts should be
    present. If about 5 volts are not present, replace defogger relay.

GRID POWER & GROUND TEST

  1. Turn defogger on. Turn ignition switch to RUN position.
    Measure voltage at left (driver side) of defogger grid. Battery
    voltage should be present. If battery voltage is not present, repair
    open circuit from defogger relay.

  2. Turn ignition switch to OFF position. Measure resistance
    from right side of defogger grid to ground. Zero ohms should be
    present. If zero ohms are not present, repair open circuit between
    right side of defogger grid and ground.

LOCATING GRID FILAMENT BREAK

  1. With engine running, turn defogger switch on. Defogger
    light should illuminate. On inside glass surface, connect voltmeter
    positive lead to power feed side vertical grid element and the
    negative voltmeter lead to ground side of vertical grid element.

  2. Voltmeter should read 11-13 volts. Connect voltmeter
    negative lead to a good ground. Voltmeter reading should remain
    constant. Using voltmeter positive lead, contact each grid at grid
    centerline.

  3. Voltage reading should be approximately half the previous
    reading (about 6 volts). A reading of zero volts indicates a break in
    the grid between positive voltmeter lead (centerline) and ground. A
    reading of 12 volts indicates a break in the grid between power feed
    side and centerline (or positive voltmeter lead).

  4. To pinpoint break, move voltmeter positive lead left or
    right along grid until a sudden change in voltmeter reading occurs.
    That indicates the exact location of grid filament break.

ON VEHICLE SERVICING

GRID FILAMENT REPAIR

  1. Mark location of broken or open grid on exterior surface
    of glass using a marking pen. Using fine steel wool, lightly rub area
    to be repaired inside rear window. Clean area using alcohol.

  2. Place 2 strips of masking tape to inside surface of rear
    window, above and below break in grid. See Fig. 3. Thoroughly mix
    conductive epoxy. Apply epoxy on grid break, overlapping both ends of

break.

3) Carefully remove masking tape from grid line. Allow epoxy to cure 24 hours at room temperature or use a heat gun for 15 minutes. Hold gun about 10" from damaged area.

G92A01033

Fig. 3: Repairing Defogger Grid Courtesy of Chrysler Motors.

REMOVAL & INSTALLATION

DEFOGGER SWITCH

Removal & Installation (Cherokee)

Disconnect negative battery cable. Remove instrument panel bezel. Remove switch housing panel. Disconnect switch connector. Depress switch mounting tabs, and remove switch. To install, reverse removal procedure.

Removal & Installation (Grand Cherokee And Grand Wagoneer)

  1. Disconnect negative battery cable. Remove ash tray. Remove
    6 screws retaining center cluster bezel. Remove center bezel. Remove 2
    screws holding dash pad located behind top of center bezel.

  2. Pry defroster grille out of dash pad. Unplug sensors and
    set defroster grille aside. Remove 4 screws in defroster duct opening
    holding dash pad. Remove 3 screws above instrument panel cluster
    holding dash pad.

  3. Open glove box, and remove 2 screws holding dash pad.
    Remove dash pad by pulling upward and unsnapping end clips. With
    drivers door open, remove one screw from side of lower trim panel.
    Remove one screw from bottom of lower trim panel and pull panel off.
    Ensure clip holding lower trim panel to instrument panel is
    disengaged.

  4. Remove 4 screws holding steering column cover. Remove 3
    screws holding bottom of bezels. Remove 2 screws holding top of end
    bezel and switch pod bezel. Remove end bezel. Remove 2 screws holding
    left side of switch pod bezel. Remove 3 screws holding right side of
    switch pod bezel.

  5. Pull switch pod bezel out far enough to remove switch
    connectors. Disconnect connectors from each switch pod and remove
    bezel. Remove switch screws and switch. To install, reverse removal
    procedure.

Removal & Installation (Wrangler)

Disconnect negative battery cable. Remove 6 instrument panel shroud screws. Slide shroud toward steering wheel. Remove 3 defogger switch bezel screws. Disconnect defogger switch connector. Squeeze ends of switch to release plastic retaining fingers. To install, reverse removal procedure.

DEFOGGER RELAY

Removal & Installation (Cherokee & Wrangler)

Rear defogger relay is Red and located behind instrument

panel, to right of steering column. Remove lower instrument panel trim

panel. Remove relay from connector.

Removal & Installation (Grand Cherokee And Grand Wagoneer) Rear defogger relay is Red and located in relay center, in glove box. Remove relay center cover. Remove relay from connector.

WIRING DIAGRAMS

See appropriate chassis wiring diagram in WIRING DIAGRAMS.