2003 Jeep Grand Cherokee Logo
Posted on Dec 01, 2008
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2001 Jeep Grand Cherokee Radiator Fan Doesn't run

Fan doesn't run at all causing the tranny and engine to overheat. Doesn't come on with A/C compressor either. Hot wired the fan and it is good. 40A fuse is good. Replaced the solid state fan relay under the headlight. No change. There are no temp sensors on the radiator that I could find though I thought that was a weak idea since the A/C doesn't bring it on either. The harness seems undisturbed and in good shape as much as I can tell. The fan appeared to have been replaced prior to my buying the car at 122000 miles. The relay was original. There appears to be power at the plug for the fan both when the key is off and when the engine is running but it must be some sort of phantom power since the fan doesn't run when connected.

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Marvin

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  • Posted on Dec 01, 2008
Marvin
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Have you confirmed the fan has a good ground, sounds like you have eliminated the issue of 12 volts, when you turn on the fan then the AC does the compressor run? if the compressor runs pull the plug to the fan motor and check to see if has 12 volts with a test light, wait for moment because the fan may not run until the AC system pressure reaches a certain pressure point, this means that even though the compressor is running the fan may not always run, There is a quick test for the fan circuit, disconnect the fan sensor at the thermostat housing, the fan should come on, this is failure mode, so if the switch goes open the fan will run to keep the engine from overheating , let me know after the tests are run.

  • Marvin
    Marvin Dec 01, 2008

    Correction, when you turn on the AC wait a moment (remember fan may not be energized until pressure builds in AC) and then test for 12 volts and a ground at the fan motor, connector, jumper acroos the connector with a test light, if there is a ground then the light will illuminate

  • shiltgen Jan 22, 2011

    I have the same issue when I pulled the plug off the housing the fan runs and once in shuts off does this indict the sensor is bad or the relay? Thanks

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Hi Dan, Yes power is always at the fan, the circut is completed by grounding. Near the thermostat housing there are 2 sending units, 1 for the gauge, on for the fan. With the key on,unplug one at a time and check the gauge to find which one is for the fan. Replace the sending unit! Frankster016

  • Anonymous Dec 03, 2008

    OK the fan does work! Not a ground prob! The prob needs to be the fan relay! You will find this in the fuse panel. Not sure of the colour, but about an inch square.Frankster016

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Is the fan motor perfect check that first.if the motor is faulty it will stop the fan to run.also try cleaning the motor and see.

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