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1999 Cherokee Sport - cooling fan running when jeep is off


 
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bga104
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Joined: 15 Oct 2007
Location: Alameda, CA

PostPosted: Mon Oct 15, 2007 7:45 pm    Post subject: 1999 Cherokee Sport - cooling fan running when jeep is off Reply with quote

I have a 1999 Jeep Cherokee Sport. I was in the Rocky Mountains a few months ago and my fan would continually run when I shut the car off. It was not necessarily when the car was hot. Once I got back to sea level, it stopped doing it for a while. I was at elevation 2 weeks ago, and it started again. This time it hasn't stopped, killing my battery twice already. It doesn't seem to happen when i have the inside fan turned off, and sometimes i can turn it off an on and "trick" it into shutting off. Sometimes not. I had the coolant temperature sensor and relay replaced and, with the inside fan running, the fan continued to run (though not blowing air inside). It's only the fan that runs, nothing else.

I am now being told that Chrysler told the mechanic that the Powertrain Control Module (PCM) needed to be tapped (as in hit lightly with a hand) to make it work. According to the shop, the fan problem seems to have been fixed (with the tap, re-programming the air conditioning clutch, and reprogramming the fan control). Now I am being told that my PCM is totally out of whack, reporting timing of 25deg one secone and -15deg the next, as well as getting input from the oxygen sensor that says to run lean one second and not the next. Supposedly, this is a problem with the PCM, and not the actual car operation, so it is not presenting itself as a check engine or in any other way (like the engine running rough). They say that the PCM port is the problem, no actual problem with the PCM. But the fan still runs.

So, i have a new coolant temp sensor, new relay, the coolant temp sensor and AC clutch have been reprogrammed, and my fan still runs when i shut it off. What should be my next step? Any ideas? Is this a known jeep issue? Thanks!
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Orangeamc13
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Joined: 20 Feb 2006
Location: East Springfield, Massachusetts - U.S.A.

PostPosted: Mon Oct 15, 2007 8:07 pm    Post subject: Reply with quote

I would install a switch to turn the fan on or off manually! Mr. Green
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bga104
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Joined: 15 Oct 2007
Location: Alameda, CA

PostPosted: Mon Oct 15, 2007 8:33 pm    Post subject: Reply with quote

a switch is an option .. i'd prefer it work correctly though!
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Tardis
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Joined: 07 Aug 2004
Location: Ohio

PostPosted: Tue Oct 16, 2007 7:14 am    Post subject: Reply with quote

bga104 wrote:
I am now being told that Chrysler told the mechanic that the Powertrain Control Module (PCM) needed to be tapped (as in hit lightly with a hand) to make it work. According to the shop, the fan problem seems to have been fixed (with the tap, re-programming the air conditioning clutch, and reprogramming the fan control).


If you have to hit the PCM to shut the fan off then obviously there's a problem with it. Replace the PCM.
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