Helping a friend. Cooling fan will not run on a 2003 Jeep. If you go from battery to fan, it runs. He checked the fuse (40 amp), OK. I suggested a fan relay. He said he thought about that, but where is it??
I also thought back to a Audi I had that would go through fan speed resistors. 2 questions… Any ideas on why the fan don’t run?? Where is the fan relay located ?? Thanks !!!
The fan motor is obviously OK, since it runs when you hook it straight to the battery.
The relay, wiring, or temperature switch could be bad. I don’t know where they are. A Haynes manual, or similar, would probably help you and your friend figure out where all of these things are.
Look for a plastic box under the hood. Many of the relays might be in it. The names of the relays may be on the underside of the lid. You might use two screwdrivers to “encourage” the relay to come out. Often, several of the other relays are the same. Look at the numbers on the relays. If they match, one of them could be swapped (maybe, the horn relay?) for the fan relay. A coolant temperature sensor gives the turn-on signal to engine computer, or the relay directly.