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Thread: 2000 Cherokee rear defroster

  1. #1

    Icon320 2000 Cherokee rear defroster

    Trying to find out if any body else has had this problem. One week the defrosters working then next it is not Went & changed the toggle switch to no avail. checked al of the fuses , none are blown. there is continunity across the defroster window grid. Any other ideas? By the way the fuse for the defroster is #12 - 10 amp fuse.
    Last edited by lunghd; 12-12-2010 at 07:26 PM.

  2. #2

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    Hi,

    Check if the switch is getting 12V, then check if its output gives 12V.
    if both are positive, search for the problem in the wiring from the switch to the window.
    if there is 12V in and no out - switch is bad.
    otherwise, check why the switch is not getting 12V, fuse or wiring in fuse area?

    Saar.
    2001 XJ Classic, RE 3.5, 245/75/16 Copper STT
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  3. #3
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    Not sure if the wiring has changed on the 2000 vs 1998, but I have done extensive testing with a VOM using the FSM.
    There is a relay that uses a switched ground inside the passenger kick panel to energize the rear window defroster grid. The grounding circuit goes from the defroster switch thru a timer attached to the back of the instrument cluster and then to the relay in the kick panel.
    On my 1998 the timer has stopped functioning and doesn't complete the grounding circuit. The timer cannot be removed from the instrument cluster and it's easier to just add a switched ground to energize the defroster relay.
    Last edited by CharlesS; 12-12-2010 at 04:05 PM.
    98 XJ 4.0L, AX-15, NP231 w/4.0:1, 4.56s D30 w/ARB, Corp 8.25 w/disc brakes and Detroit No-Spin, 32x11.50 MTRs

  4. #4
    Moderately Senior lunghd's Avatar
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    Cool tip! Is there any easy way to just jumper around the cluster and eliminate the timer from the circuit? If it's a simple jumper wire installation around that timer then the OEM switch etc would retain control over the rear defroster without a timer circuit as the early XJ's do.

    Is the OEM defroster timer (in the cluster) electronic or mechanical? (I'm guessing electronic but given some of the factory kludges they've done over the years I can see them using some leftover wind up alarm clocks...) Any idea what years use the same set up?
    "...the advice given above is somewhat arrogant and in some cases wrong..." . (I'm not an expert... I just play one on the internet.)

    Another Freakin' Jeep Cherokee Website. _____________ Sure you're smart... but do you have what it takes to make "The List"?


    1990 XJ

  5. #5
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    I haven't inspected all the years of the 97-01 XJ clusters, but the years that I have checked (97,98,99 and 00); they all have an electronic timer. It is a round black plastic component soldered to the back of the cluster about the size of a quarter and about 1/8" thick.

    The problem with jumpering around the timer would be that the rear defroster switch is not a snap switch, it doesn't stay engaged and not having a schematic of the instrument cluster I wouldn't know what else that jumper might affect.
    The timer holds the ground to the relay coil for a certain amount of minutes and then releases so you don't cook the defroster grid.
    If you do wire in a switch and ground wire as I suggested; I would also suggest you cut the factory ground wire for the defroster relay.
    Last edited by CharlesS; 12-12-2010 at 07:38 PM.
    98 XJ 4.0L, AX-15, NP231 w/4.0:1, 4.56s D30 w/ARB, Corp 8.25 w/disc brakes and Detroit No-Spin, 32x11.50 MTRs

  6. #6
    Moderately Senior lunghd's Avatar
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    Cool - so a reasonably talented person could fiddle with this, unsolder the timer, determine the jumper points & be rid of it. (Yeah - a lot of trouble but there are some of us who'll waste an entire month in the garage if it keeps us from doing real work. )

    Thanks for the response - there are a lot of things like this that are different than my old RENIX XJ so (short of buying a newer XJ) the only way to learn is through the experience of others.
    "...the advice given above is somewhat arrogant and in some cases wrong..." . (I'm not an expert... I just play one on the internet.)

    Another Freakin' Jeep Cherokee Website. _____________ Sure you're smart... but do you have what it takes to make "The List"?


    1990 XJ

  7. #7

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    Found something else today concerning the wiring Thr ear defroster also has a common white wire with the rad cooler fan and O2 sensors so if problem with the defroster check also fuse #14 & 12. The codes staart kicking out P013 , P0136 & P.1452 Right now I may be looking at a new PCM. Fun time/

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