Goliath442

i have a 2000 jeep cherokee. the cooling fan works, the relays seems fine and the cooling sensor has been changed.. cooling fan will run if cooling sensor not pluged in.. as soon as you plug snesor on thermostat housing in, cooling fan shuts off..this is with air conditioner on and at operating temps. 4 liter 6 cylinder.

4WD4EVER

Jeep changed the parameters for when then aux fan would turn on in 2000. There must be either a certain amount of pressure in the a/c system or the coolant must reach ~223°F. Once either one of those conditions is met, the aux fan will then turn on.

Plug the coolant temp sensor in, wait for a hot day or run the Jeep hard and then let it sit and idle for awhile. Chances are it will kick on. Remember, if neither of the two aforementioned conditions is met, the aux fan will not kick on in a '00-'01 MY.

dave1123

This is not an aux fan, but the only fan a 2000 4.0 has. On initial startup, it won't run until the coolant reaches 215*, then kicks on high. When it drops to 195*, the fan runs on low until the coolant again reaches 215*, cycle repeating. It will run on low as long as the engine runs until you shut it off. It's supposed to run on high whenever the A/C compressor clutch is engaged as well. The temp sensor only sends info to the PCM. The PCM then sends commands to the relay and temp gauge. The temp sensor is just a variable resistor. It's possible you got a bad sensor off the shelf...or the wrong one. It should read between 11,370 and 13,610 ohms at 68*F.

This took a while to sink into my brain. None of the gauges are hooked directly to sensors. It all comes from the PCM interpreting the sensor data. This all began in 99 with the installation of the CCD Data Bus.

This is what it's supposed to do. If it's not, I haven't a clue where to start.

mailmom32

Hi, so I'm having a similar problem but it started after we changed the ac compressor. The jeep ran at 210, with the ac on. Electric fan would kick on at 210 and go back off. The compressor was bad (making a terrible noise) so we changed it. Took to the shop, had lines vacuumed and refilled. Well, the shop called and said the fan wasn't coming on with the AC and we should hook up a toggle switch. I did some investigating and found the 2000 xj fan doesn't come on automatic with the AC. So, I ran the jeep today on a mail route and it was 85+ outside. When I turned the AC on the temperature climbed above the 210 mark, just barely, after a short time. Maybe 213 or so.

My question Is, why didn't it do that with the old compressor?? I haven't changed much in relationto this. Only thing has been the radiator and the electric fan. I have a transmission cooler on there.

But, being it only got to 210, In same driving conditions, before the compressor change, I'm not sure why it's climbing now.

Any ideas ?? Is it ok to be that warm? Im not even sure what thermostat is in it. Probably whatever the part store recommends.

Thanks!