there may be a Inline Fuse somewhere in the harness....A diode is something that allows elec current to flow only one way.

Does the dash guage work?

 

Like i said in post #2, people have said '00-01 XJ efans don't kick in when a/c is on like it does on previous years. 00-01 efans are temp sensitive (223F) and refrigerant pressure sensitive.

 

I realize this is an old post, but this is for anyone that finds it online. The '00-'01 XJ fan certainly doesn't come on unless the ECT reads 218F or higher, or the AC high pressure switch is made (sorry don't know the pressure). So don't expect it to run just because the AC is on.

 

not sure about this,
in my case I got a 2000 XJ and the E-fan kicks in everytime I set the AC to on, eventhough there is no refrigerant in the lines, but the position of the switch is enough for it to turn on. (while turning it to the non AC positions, or using the Defog setting)

 

Now we have controversy..........get those '99 and '00 FSMs out and let's get this confirmed/settled.

 

According to the this diagram:
http://www.justanswer.com/jeep/37nvy...g-diagram.html

When the AC switch is on the AC positions, the signal passes through the A/C high pressure switch, and then requests the PCM for the e-fan to run.

On my case I think the High Pressure Switch on the AC line is bypassed, that is why the signal gets to the PCM.
I think the OP should check the wiring from the AC control switch to the High Pressure switch, and then to the PCM, we already know from the PCM to the Relay is working fine as when he removes the connector from the Temp Sender the E-fan kicks in, so the failure should be before the PCM

 

So, u r saying your '00 has been modified/changed from OE Factory.

 

In a word YES, the pressure switch on the AC has been bypassed.
I went out and confirmed this when I saw the schematics, so in my case from the AC controls the signal goes to the pressure switch, bypassed and to the PCM which will sent the signal to the relay and then to the e-fan.

So if the OP AC system is appropiately charged, the signal should flow to the pcm, and then to the relay and the fan.

I'm thinking the either the AC pressure switch is faulty, or an electrical line is broken, hope it helps

 

These Diagrams May Aid You.

 

So we r back to OE Factory is '00 up the efan is a/c system X amount of pressure activated and '99 down the efan is a/c compressor engaged activated.......along with coolant temp activated.

 

Here's a schematic showing the 00/01 AC pressure switches.</p>

 

Wow. You guys are awesome. I'm new to the forum, but just wanted to chime in. Thanks for all of the clarification and details. I just picked up my 2000 XJ a few weeks ago. Nice basic transportation. Had to get an automatic after a motorcycle wreck, doubt I'll ever be able to push a clutch pedal again unfortunately.

 

In my 2000 XJ the fan does not automatically come on when the AC is activated, so it's temp or pressure based as was previously indicated.

 

Below is an explanation of how the 2000/2001 AC system works.


And a schematic of the switching system.


If the pressure in the refrigerant system is too low the fan will not turn on.


To test the AC system you can remove the Low Pressure Cycling switch connector and jumper the two pin cavities in the connector with a paper clip, select an AC function on the Mode Selector Switch, and start the engine. The fan should run and the AC Compressor Clutch should engage.


If the coolant temp never gets to around 223*F the fan won't turn on.
.

 

I have a bone stock, non-modified 2000 Cherokee and have confirmed the electric fan does NOT come on until the temp gets over 220. I turned on the A/C and let it idle in the driveway for a long time. No electric fan, no electric fan, no electric fan, temp goes over 220, BAM!, electric fan comes on.

I don't like sitting at a stop light and watching the temp gauge climb to to over 220 before the fan comes on, but apparently it's not a problem if the computer was programmed this way. I'm not wanting to mess with the electrical system to change it.