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Unread 06-17-2008, 07:58 PM   #1
ntaousakis
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Electric Fan? What Temp Does yours turn on at?

I replaced my relay since the fan was not working with the A/C on when I checked. Its turns on when the A/C is on, but with the A/C off, it turns on after the temp gauge reads approx: 220 degrees, 1/8 past the 210 mark. I would think the fan is supposed to turn on at the 210 mark or prior to it. Anyone have any feedback on this?

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Unread 06-17-2008, 08:22 PM   #2
CMARJEEP
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probably a bad temperature sensor....
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Unread 06-17-2008, 08:30 PM   #3
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probably should get a turned on at 195 or so. currently mines not turning on at all. so i just gotta keep moving to stay cool lol
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Unread 06-17-2008, 10:24 PM   #4
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Mine turns on at about 212 and immeadiately goes down to about 208
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Unread 06-17-2008, 11:48 PM   #5
ntaousakis
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so the electric fan uses a separate temperature sensor than the one that my gauge uses?

I always remembered my gauge being at 210, never above, well until the fan became inop since the relay #2 went bad. Could it possibly be the relay again? I know its supposed to have a low and high speed, maybe the low isnt working, and only high is, and the high kicks on later?
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Unread 06-18-2008, 12:31 AM   #6
drums4abyss9139
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yeah mines having the same problem...my fan won't turn on and if i idle for too long the engine overheats...idk how to approach it or what is causing the fan to not turn on
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Unread 06-18-2008, 05:55 PM   #7
ntaousakis
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mine turns on, but I think its turning on late. Im thinking there are two speeds, high and low, and the relay controls this. Possibly, my new relay is bad, and is only sending the high signal? Does this make sense?
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Unread 06-18-2008, 08:21 PM   #8
indept
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Quote:
Originally Posted by ntaousakis View Post
mine turns on, but I think its turning on late. Im thinking there are two speeds, high and low, and the relay controls this. Possibly, my new relay is bad, and is only sending the high signal? Does this make sense?
Its a pulse width modulated system which means it pulses on for some fraction of a second then off again. By making the on pulse wider (longer on time) in relation to the off part of the pulse, that gives you the higher or lower speed. So to answer your question, NO it doesn't make sense since it's the same output on the relay for high & low.

When you take it apart to check or replace the relay, check the connector. My connector was fried due to overheating and one of the pins was black & the plastic section of the connector was cooked. The dealer sells a repair kit for it for about $15. You just splice in the new connector.
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Unread 06-19-2008, 06:20 AM   #9
ntaousakis
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ok. Ill have to do some more testing I suppose. I know the fan does work since it turns on when temps get hott, and when the A/C is on. My Mechanical fan seems to be working. I did notice that the mechanical fan and the electrical fan spin opposites in direction. From the drivers seat point of view, the electrical fan spins counter clockwise, and the mechanical fan spins clockwise
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Unread 06-19-2008, 06:29 AM   #10
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[QUOTE=indept;5354540]Its a pulse width modulated system which means it pulses on for some fraction of a second then off again. By making the on pulse wider (longer on time) in relation to the off part of the pulse, that gives you the higher or lower speed. So to answer your question, NO it doesn't make sense since it's the same output on the relay for high & low.

When you take it apart to check or replace the relay, check the connector. My connector was fried due to overheating and one of the pins was black & the plastic section of the connector was cooked. The dealer sells a repair kit for it for about $15. You just splice in the new connector.[/QUOTE

I highly doubt the jeeps cooling fan uses Pulse width Modulation. Especialy if it is controled by a relay, first off a realy is not going to switch power fast enough to use PWM second you would burn up that relay in a month switching it on and off. The may very well contain two contacts allowing one to swithc high speed and one to switch low speed. Just about every cooling fan I have come across has two wires one for low and one for high speed.
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Unread 06-19-2008, 07:47 AM   #11
Bob D.
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Quote:
I highly doubt the jeeps cooling fan uses Pulse width Modulation.
According to the factory manual the electric fan does use PWM.
But it's essentially a two speed fan. The PCM receives input from the temperature sensor then instructs the relay to turn the fan on low, high or off. The module/relay is out of the loop for speed and on/off changes, ie all speed and on/off commands come from the PCM, the relay merely carries out the instructions from the PCM and nothing more.

On the 4.0 liter the electric fan should come on LOW slightly before the 210 degree mark, (or at any temperature when the a/c is activated) HIGH slightly after.

On the 4.7, the mechanical fan is the primary cooling fan and should handle most cooling demands, the electric fan should run when the gauge moves over the 210* mark.
The idea is to keep it as close to its optimal operating temperature as possible.

If the electric fan turns on just after 210 degrees it's working properly.
Make sure the mechanical fan is doing its job - locking up fully when it should.
If you rule out the above scenarios then the problem is not the fan/s.

Note:
All underlined text has been edited for clarity.

Last edited by Bob D.; 06-19-2008 at 08:58 AM.. Reason: Edited for micifus
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Unread 06-19-2008, 08:10 AM   #12
micifus
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Quote:
Originally Posted by Bob D. View Post
According to the factory manual the electric fan does use PWM.
But it's essentially a two speed fan. The PCM receives input from the temperature sensor then instructs the fan to turn on low, high or off. The module/relay is out of the loop, ie all speed and on/off commands come from the PCM.

On the 4.0 liter the electric fan should come on LOW slightly before the 210 degree mark, (or at any temperature when the a/c is activated) HIGH slightly after.

On the 4.7, the mechanical fan is the primary cooling fan and should handle most cooling demands, the electric fan should run when the gauge moves over the 210* mark.
The idea is to keep it as close to its optimal operating temperature as possible.

If the electric fan turns on just after 210 degrees it's working properly.
Make sure the mechanical fan is doing its job - locking up fully when it should.
If you rule out the above scenarios then the problem is not the fan/s.
Haha ok I believe you why is ntaousakis replacing relays then?
There is or is not a relay?
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Unread 06-19-2008, 08:24 AM   #13
Bob D.
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Quote:
Originally Posted by micifus View Post
Haha ok I believe you why is ntaousakis replacing relays then?
There is or is not a relay?
Not sure what you are implying - of course there is a relay for the electric fan, where did I indicate otherwise?
As far as the OP, relays just go bad. Why he had two in a row fail, your guess is as good as mine...

Edit:
micifus, I clarified the part I think you were objecting to.

Last edited by Bob D.; 06-19-2008 at 08:44 AM..
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Unread 06-19-2008, 09:35 AM   #14
micifus
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ok its a solid state realay so I believe you.
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Unread 06-19-2008, 11:47 AM   #15
indept
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yes it is solid state, which is why they get replaced. Don't get me wrong, solid state relays are very depedable and should last longer than the Jeep...IF DESIGNED CORRECTLY, which is the problem. Where the WJ's have it mounted is bad. The relay gets VERY hot and heat is the worst thing for solid state devices. When I replaced the burnt connector on mine I ran it and the relay got too hot to touch so I lengthened the harness & moved it in front of the AC condenser just behind the grill. I mounted it to an old pentium heatsink and mounted it with the heatsink fins in the airflow. (I painted it black so you can't even notice it). Now it runs cool to the touch. I did that about 2 years ago and have had no problems with it.
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