The electric fan relay is USUALLY the suspect in cooling related problems on electric fan-equipped 4.0L WJ's. If you take it to the dealer, be prepared to pay. The authorized way to replace this relay is to pull the entire from bumper cover to gain access. The relay is located under the passenger side headlight. The shortcut is to cut an access hole in the plastic under the headlight.
I wish I could show you the authorized method and how to cut the access hole, however when I went to replace my fan relay (for the second time), I found that the dealer who did the work previously had cut a hole for me already - even though I was charged labor for them to remove the bumper cover.
For this second relay change my WJ has experienced now, my symptoms were simple to diagnose. My engine fan would remain on after shutting off the vehicle. Fortunately, I was the one driving the vehicle when this started happening (not the Mrs.). Basically, something goes awry in the fan relay, allowing a constant stream of 12v power to reach the fan - regardless of ambient temperature or key position. I promptly returned home and disconnected my negative battery cable to shut the fan off.
- Remove the negative battery cable from the battery.
- To cut the access hole for the relay, first you must remove the passenger side headlight. To do this, remove the jackscrew from the top of the headlight. The jackscrew is directly on top of the headlamp and does NOT screw into the radiator core support (see pic below). After the jackscrew is fully removed (this screw is roughly 6" long), grasp the headlight assembly and forcefully pull the headlamp outward. Unplug the headlight wiring harness. Notice the exising hole in plastic under headlamp on my WJ.
- Unscrew the two screws holding the relay to the body.
- There isn't alot of slack in the wire, but enough to pull the relay out of the hole and disconnect it. Note that the electrical plug has the same sort of locking clips as other locations in the engine compartment. Use caution releasing the locking click to avoid breakage.
- Connect the new relay to the wiring harness. Be sure it is firmly seated.
- Attach the relay to the vehicle body in its previous location.
- Reconnect the headlamp wiring harness.
- Insert the headlamp back into its original position.
- Reinstall the jackscrew in the appropriate hole. Be sure to apply some pressure to the bottom of the housing while doing this to assure the jackscrew passes through the retaining loop on the back of the headlamp. If you miss this retaining loop, you run the risk of breaking it off when tightening the jackscrew.
- Reattach the negatie battery cable to the battery.
- Start the vehicle and let it idle until normal operating tempurature is reached. You should hear the electic fan kick on around 210°.