Radiator Fan Madness.....

Hello all,

I have a black 2001 Jeep Cherokee Classic auto with 51k miles on it. It always runs great and haven't had any major problems. I have a minor problem now. My radiator fan never kicks on, ever. A couple days back on what was reported to be the hottest day of the year (at noon no less) I idled my vehicle while waiting for an associate for about 10 minutes. I then began driving away and about 1 mile down the road my vehicle lost a lot of power and began shaking, and my oil pressure pinned to 80. I immediately pulled over, popped the hood and checked around and waited 5-10 minutes before starting again... everything goes back to normal. So I begin pining throught he various forums looking for reasons for this as my engine temp never went over 208 while this happened. Someone suggested that it could have been that my radiator fan had bit it; they had a similar problem and found it to be the case. So I have been checking at various temperatures at various times of the day and he's right, my radiator fan never comes on.

The first thing I do is check my fuses (under the hood by the coolant reservoir and inside the vehicle by the passenger side door) and none are blown. Next i unplug the fan and direct connect it to the battery. To my surprise the fan kicks on!

So it's not the fan, and it's not a fuse (unless there's some other place fuses are hidden). That leads my to believe the electric part of things are fine ( I go under the assumption that if it was a shorted wire a fuse would have blown). So now I go forward looking for something else: but What?

Where do I go from here? Are there sensors that could be bad that are telling it not to turn on? If so, where? Could it still be a bad wire (I haven't found a voltmeter to check the plug to see if current is coming to the fan). I believe that the fan has not been coming on for some time and things have been fine with the exception of it being so uncommonly hot on that day. Any suggestions as to where to go next?

thanks in advance.

The fan don't come on untill 217 f. Check your engine codes.

As stated by langer1, I think you're barking up the wrong tree. Your electic fan is not coming on because you are not overheating. That is a VERY good thing. There is something else going on,... maybe a CPS going bad which they do.

Does the electric fan come on with the A/C compressor? Does your Jeep have a mechanical fan and an aux electric fan?

It's probably not the CPS. When those go, generally it's a complete loss of fire.

Does your A/C work? The aux electric fan should come on with the A/C, that's an offroader trick to force cool.

Start by checking your engine codes with a scan tool.

you say you checked the fuses, but did you check the electric fan relay, I have one of those too. Sounds to me that if you think it is that hot and its not cutting on, but if you direct conect it to the battery and it works; then a relay is thrown out.

The aux fan is controlled by an auxiliar contactor that is house with other similar units in a housing at the right side of the engine bay, try exchanging the unit (it unplugs pulling it out) with another unit and checking if it works that way.

By the way the 4.0L engine has TWO sensors, one that gives the engine temp that is located at the back of the engine near the bellhousing and the other at the water elbow conection for the upper hose that controls the aux fan, if this unit has becomed unplugged or is not working well it will never kick your aux fan on.

The first check is what others have recomended, connect your A/C (if you have one) the aux fan should start if not start checking the contactor.
Cheers

SACEM