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Unread 02-04-2006, 09:36 PM   #1
escbill
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Grand Cherokee Cooling Fan Won't Run

Whoops! Originally posted this in the wrong forum...My daughter's Grand Cherokee has a cooling fan that does not run when the engine is warmed up. The fan tests good and runs when powered up. The thermal resister on the head tests the same as a new one out of the box. Is there a relay somewhere that I can't find that is preventing the fan from coming on when required? I apologize if this has already been addressed before, but it's a new problem to us. Thanks!

The Grand Cherokee is a 2000 model with a 4.0L six cylinder engine.


Last edited by escbill; 02-04-2006 at 11:38 PM..
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Unread 02-04-2006, 09:47 PM   #2
Stocker
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Welcome from NorCal!

My ZJ has an engine-driven clutch fan, and I won't be much help. But if you mention the year of your daughter's Grand, and which engine it has, it will be easier for others to give an answer about the relay.
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Unread 02-04-2006, 09:57 PM   #3
goodolboy71
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if its a factory electric fan on a ZJ, then i would guess your daughter has a 5.9....check the fuses,and relays to the fan as well as the temperature switch...if none of that is messed up then test the fan motor, if its gone, there was a post from a few yrs ago where i guy found out the motor from a parts storew as over 150 or 200, but it was the same motor used on some ford tarus or something and that motor with the same part # was less than 100..maybe someone else can find that post, it was either here or on JU
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Unread 02-04-2006, 10:39 PM   #4
escbill
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What is working...

Quote:
Originally Posted by goodolboy71
if its a factory electric fan on a ZJ, then i would guess your daughter has a 5.9....check the fuses,and relays to the fan as well as the temperature switch...if none of that is messed up then test the fan motor, if its gone, there was a post from a few yrs ago where i guy found out the motor from a parts storew as over 150 or 200, but it was the same motor used on some ford tarus or something and that motor with the same part # was less than 100..maybe someone else can find that post, it was either here or on JU
Fan is good and works when clip lead power is applied. Thermister on head is good and tests with the same resistance as a new on in a box does. Fuses seem to be intact. Cannot locate any relays, other than those in the box under the hood, and they're all OK. Have been told there is another relay somewhere, but cannot find it and the Haynes manual doesn't mention it.

The Grand Cherokee is a 2000 model with a 4.0L engine.

Last edited by escbill; 02-04-2006 at 11:37 PM..
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Unread 02-05-2006, 11:46 AM   #5
Stocker
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A quick search turned up this thread -- HTH! http://www.jeepforum.com/forum/showt...ighlight=relay
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Unread 02-05-2006, 03:26 PM   #6
goodolboy71
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Quote:
Originally Posted by escbill
Fan is good and works when clip lead power is applied. Thermister on head is good and tests with the same resistance as a new on in a box does. Fuses seem to be intact. Cannot locate any relays, other than those in the box under the hood, and they're all OK. Have been told there is another relay somewhere, but cannot find it and the Haynes manual doesn't mention it.

The Grand Cherokee is a 2000 model with a 4.0L engine.
well if its a WJ there is a relay behind the passenger side light, factory fix is to cut/dremel a hole out and replace the relay...i think there was a link on WJEEPs somewhere showing a pic of it
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Unread 05-03-2006, 09:03 PM   #7
cifer6425
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So the Tarus fan is a good choice? If you do not drive a Honda Accord or Civic on this island it is damn near impossible to find any parts in a junk yard. However I did find a Tarus fan for 70$. This is much better than a dealer quote of $35415684 and the shipping charge if I buy an aftermarket fan and have it shipped in.

I just have a few concerns.
1) wiring it up
2) jerry rigging my Jeep. as you all call it, it is a mall crawler. just something to transport people in. I plan on selling it when we move.
3) it actually working and keeping the Jeep cool

Any thoughts, concerns, first hand experiance?
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Unread 05-04-2006, 07:29 AM   #8
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Quote:
Originally Posted by cifer6425
So the Tarus fan is a good choice? If you do not drive a Honda Accord or Civic on this island it is damn near impossible to find any parts in a junk yard. However I did find a Tarus fan for 70$. This is much better than a dealer quote of $35415684 and the shipping charge if I buy an aftermarket fan and have it shipped in.

I just have a few concerns.
1) wiring it up
2) jerry rigging my Jeep. as you all call it, it is a mall crawler. just something to transport people in. I plan on selling it when we move.
3) it actually working and keeping the Jeep cool

Any thoughts, concerns, first hand experiance?
Sounds like cifer has a bad fan relay...

Regarding Taurus fans...

I had a couple of Taurusussssssusssusss or is it Tauri? One was a 3.0 the other was a 3.8 wagon. The 3.0 is a simpler design that used an external resistor to control high/low speed. The 3.8 has three terminal motor with two sets of motor windings, one for low speed, one for high speed. I would probably opt for the 3.0 type fan as this is similar to the OEM jeep fan.
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Unread 05-04-2006, 08:08 AM   #9
goodolboy71
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most people use the 3.8 fan.....as far as being similar to the jeep setup.....if you own a 5.9 with the factory efan.....the fan motor is the same seimens number as the one used on the 3.8 taurus fans....if you go to the parts store and ask for the 5.9 elec fan =$$$ but the one for the taurus is less than 80.00 i think...i dont know if anyone has used the 3.0 fan yet though..
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Unread 05-04-2006, 02:24 PM   #10
cifer6425
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i dont think my relay is bad. when i unplug the fan, and take a volt reading going back to the relay, i am getting ~6 volts. so in my way of thinking, that tells me there is power getting to the fan. when i connect the fan directly to the battery, it does not spin at all. those two factors leads me to believe its a fan problem.

although my jeep knowledge if VERY limited, and my electrical knowledge is not much better.
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Unread 05-04-2006, 03:34 PM   #11
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In your first post you said,
Quote:
Originally Posted by escbill
... The fan tests good and runs when powered up. ...
Now you are saying that it doesn't run at all. That's a little confusing.

However, the electric fan gets it power through a "pulse width modulated" (PWM) solid state fan relay. Signals for the PWM fan relay come from the powertrain control module (PCM) using a bunch of other sensor signals and determines what voltage is applied to the fan motor. Measuring the voltage output of the relay can't really tell you if it's working properly or not.

For more information, take a look at my rather lengthly second reply in this thread: http://www.jeepforum.com/forum/f13/2001-cooling-fan-268042/.
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Unread 05-04-2006, 04:11 PM   #12
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This is getting confusing because two different people are posting about the same problem. So becareful and check the names of the people that are posting.

Now for the original poster it sounds as though you have a bad relay.

For the islander, you have a bad fan motor.
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Unread 05-04-2006, 04:21 PM   #13
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The fan on your Jeep has two terminals. One is connected directly to ground. The other terminal is the positive side of the fan which is supplied as a pulsed PWM positive output from the relay. With the entire circuit intact, and the fan circuit active (you can turn on the AC to achieve this) you should measure positive voltage on the positive side of the fan. It won't be necessarily a full 12V, due to the PWM, but it shoud be at least 4 or more. If your getting low voltage during this test, the relay is most likely defective.
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Unread 05-04-2006, 08:42 PM   #14
cifer6425
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I am sorry to high jack this thread, but I did not really feel it necessary to start another thread about something so closely related.
what I did today was swap old fan motor and fan blades out, and put in a newer ford tarus motor and fan blades. the jeep fan blades will not fit over the tarus motor with out some modifications. (very simple mods, but I was at work and did not want to abuse the privilege of working on my car at work) the reason for this is to keep the stock look, and not have to fabricate a mounting system for the tarus fan shroud.

some of you all may disagree with me on this point, but I just wired up tarus motor same as the jeep motor. wiring it to come on in the high position. I will go look and see if I can get a bigger relay. but for right now its just stock

escbill have you gotten your situation resolved yet?

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Unread 05-05-2006, 11:24 AM   #15
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that's the radiator fan relay .. it's gotta be good
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