Came home from a week long fishing trip to find the wife's 01' WJ in the garage with a dead battery. She said that the fan kept running after she parked it and the next morning the battery was dead. Now having owned a few Jeeps with an electric coolant fan, I had a pretty good idea what was wrong and immediately contacted my parts guy who had a new solenoid on my doorstep in less than 48hrs. When this solenoid goes bad, one of two things happen. Either the fan fails to turn on when it should or the fan fails to turn off when it should. I've had it happen both ways in the past.
If you check the service manual for a WJ or XJ it will give you a 1hr plus procedure which involves removing the front bumper cover, vacuum tank and some other crap to reach the solenoid from underneath . A much easier and quicker method is to remove the passenger side headlamp unit and cut a hole in the plastic molding above the solenoid. Takes longer to gather up the tools to do it this way than the actual removal and replacement. About 20mins tops.
On the WJ the first thing to do is remove the neg battery terminal and then remove the single long bolt that holds the passenger side headlamp in place.
Then grasp the headlight unit firmly and pull it straight out. Nex t remove the various bulbs from the unit and set it aside.
You will now be looking at the plastic cover over the fan solenoid.
You can use whatever you want to cut a hole just big enough to reach the
solenoid but I have found that using a 1" holesaw to cut a pair of holes works just fine.
There are a pair of metal screws that hold the solenoid to the Jeep (5/16" I think) that are easily reached with a 1/4" drive socket and extension. Just be careful not to drop the screws or you might be removing the bumper cover after all.
After the screws are removed, there should be just enough play left in the wiring to wiggle the solenoid out of the hole enough to reach the wire connector. Just slide the red tab on the connector over and push down on the small level on the wire end of the connector and it should pull right off the solenoid.
Now take the new solenoid and compare the numbers to the old one just to make sure you purchased the right one.
Connect the wire to the new solenoid, slide it into place and attach it to the Jeep with the old screws or the new ones if you prefer.
Now all that remains is to put the bulbs back into the headlight housing, pop the housing back in place and tighten down the attachment screw. Attach the negative battery terminal and you should be good to go. Some folks like to tape the original pieces of plastic back on to the Jeep to prevent water from draining into the new holes. I never have and can't say it has ever caused me too much trouble.