Working on a friends 2000 Cherokee (completely stock)

Her AC keeps shutting off after stopping in traffic. So I went to check AC pressures and noticed that the eFan was not running.

* Checked fan directly to battery - Working.
* Pulled fan relay and put fused jumper across 30/87 and fan runs.
* At this point since the A/C gauges were still hooked up I let it run for a fem min and topped off the refrigerant and had nice cold air and good pressures.
* got back to the fan not running issue
* Put in different (known good) relay and fan does not run with AC.
* Found schematics in https://www.cherokeeforum.com/f2/coo...nction-133903/ (listed for 97-99 but says it's the same for 00-01)
* There is voltage at 85 when the ignition is on like the diagram shows so the cabin fuse is good (pulled and confirmed it anyway)
* on a volt meter there is ~13v between 85 and 86 when running and AC turned on (again like diagram shows)
* if I connect a relay when the voltage is present the relay will flash on but not stay on and the voltage drops to 0.2 until the relay is removed from the circuit then goes back to battery level.
* So I was thinking the PCM has issues and can't supply the current needed to energize the relay.
* But then I pulled the Coolant Temp sensor and the Fan does turn on. So the PCM can turn it on.

Was thinking about bypassing the PCM and connected a jumper from the C48-18 TN (tan wire from the high pressure switch) to the ground (86) the fan turns on/off as expected, but it throws a CEL and she would loose the overheat eFan turn on.

So my options are a new PCM or figure out something that won't trigger a CEL.

I thinking of the option of:
* Splice into the DB/PK (86 on the relay) with a diode set so it won't back feed the PCM from the Tan wire (mentioned above). So either the overheat or the AC on conditions will turn on the fan.
I want to know if anyone else has done this or knows any other fixes to try.

Thanks in advance!

 

On a 2001, and possibly a 2000....the fan is not tied in to the ac like in 1999 and below. The fan is only driven by temperature. If you disconnect the sender in the thermostat the fan should run. Oh i see you did that.... The ac high pressure switch has 2 contacts. One turns off the compressor, other one turns on the fan. If you cut and directly jumper together the fan will run whenever an ac mode is selected OR you can run those 2 wires to a toggle switch and choose when you want the fan when in an ac mode

 

I've never heard of a vehicle that didn't run the fan when the ac is on at least at low speed. How are you supposed to test/adjust refrigerant levels if the radiator isn't being cooled properly. Sounds like a huge fail on the design.

Knowing the driver I think I'll just jumper the fan side of the switch she wouldn't remember to turn another switch on/off.

Thanks for the help.

 

They cared more about emissions then you overheating. The 2 wires are light green and tan one above the other. The light green and blue/pink is for compressor cutout. When connected together, the fan will run any time an ac mode is selected

 

Used a crimp on splicer to jumper the 2 wires.

 

Well, if you want to do things the easy way...never trusted a splice or crimp that you couldn't verify the actual contact points but we're not talking any real current. Does it function as you wanted

 

Been working so far. It's only a signal line not the current the the fan so I think it will be ok.