cwikk

Hey guys, newer to the forum so I didn't know where to post, but I got an 01 Cherokee with almost 400,000 Km's on it and a while ago my electric fan just stopped working on me, I tried everything so far and it sometimes works intermittently but never reliably. I've replaced the thermostat, the rad cap, the radiator, the coolant temp sensor, the mechanical fan and flushed the whole system many times just to make sure it wasn't just cause crap was in the system, and I've already checked the relay, the fuse and the fan itself. I'm so stumped on this cause every so often it works and then I leave it running sometimes and it over heats on me cause it didn't kick in. Any help would be awesome.

FruitSnacks

Your jeep shouldn't over heat just because the electric fan doesn't work.
I have mine hooked up to a switch and i only use it when i use my a.c. (which is rare) and mine runs normal operating temp. Fan is supposed to come on with a.c. and at a certain temperature ( can't recall for sure). I would say to check your wires. You should have seen the hack job the PO of mine did to the elec fan wiring; tape, wire crimps, and a whole lot of other unnecessary **** just to keep the fan going.

mikesignal

I think it is supposed to come on at 218, and with ac, but not 100% sure about the ac exactly....but it is supposed to cycle on and off with temperature, and not stay on all the time.

Turbo X_J

If there is 12V @ the fan & still no fan, it's the fan, man.

Muddz

Is it a newer fan?

Those fans eventually "start" to wear out, seem to operate ok when running but have actually become weaker. It's sometimes difficult to determine as the aux fan seems to run normal but actually not put out enough air flow - cfm. After more use the aux fans eventually slow down where it's more noticeable that their failing. I once had this problem while on the trail and steep inclines, the engine would overheat. Replacing the aux fan fixed the overheating problem.

Your problem sounds different as the fan works sometimes, it's possible the fan itself is working intermittently and needs to be tested directly connected to 12 volts for on and off operations. With age these fans sometimes only work intermittently, signs of a failing fan.

I'd probably first remove the fan and check the plug connectors, making sure there's no corrosion, bent/pulled pins. Testing the fan making sure it turns on and off when 12 volts is applied and removed. Also the aux fan relay, these sometimes will work intermittently. And all the wiring going and connected to the circuit for the aux. fan. (if you have AC you can test the relay voltage output to the aux fan with a meter, the aux fan is suppose to turn on under certain condition while the AC is on, 00 and 01 some changes were made to the aux fan PCM programming, I can't remember off-hand the specifics of the programming)

What I did for my aux fan is install a manual over-ride switch. Wired from the battery to a 30/40 relay the aux. fan turns on from a manual switch or the PCM.

The PCM can't predict many engine and terrain conditions. While under certain conditions e.g. sand & high heat. I manually turn on the aux. fan before reaching 218 deg. F. Engine cooling is usually more efficient as under some types of conditions when the aux. fan turns on at 218 deg. F the coolant will heat up much higher ~225 - ~230+ and the cooling system has a difficult time trying to cool the engine back down. Turning on the fan at lower temps the engine coolant temps may still go up but not as high and it becomes less difficult for the cooling system to cool down the coolant and engine.

extrashaky

Nope! The fan does NOT automatically come on when you turn on the AC in the 2000 and 2001 XJs. This was a change in design for the 2000 model year that does not apply to earlier models (hence the frequent confusion). Normally the fan comes on when coolant temp is 223° F and goes off when it drops below 217° F. The AC only calls the fan when the dual function pressure switch in the AC system senses reads a pressure of 300 psi and stays on until it drops below 235 psi. Any other time, the fan will be off, even if the AC is on, leading people to believe their perfectly functioning electric fan has failed.

CCKen posted some excellent information about this system in the thread below, including how to jump the connectors on the dual function pressure switch to test its operation.

https://www.cherokeeforum.com/f2/coo...nction-133903/

Does it overheat while you're driving, or only when it's sitting still?

If it overheats only when you're sitting at idle, that's usually a symptom of a bad fan clutch. I know you said you replaced it, but there have been stories on here of people getting bad fan clutches new out of the box. If you test the electric fan per CCKen's instructions in the link above and still can't figure this out, you might take another look at the fan clutch.

cwikk

Thanks for all the help guys, my fan does have a good connection and I know this because if I unplug the temp sensor the computer automatically turns the fan on to prevent over heating. I know it's not working right though because when it works my jeep can stay idling in traffic in the hottest day and still be fine, but as soon as it doesn't work the rad starts to boil over and coolant pushes out the rad cap and fills the reservoir right to the top.

FruitSnacks

It shouldn't overheat just because your electric fan doesn't work. Like i mentioned before, i don't use mine and it runs normal operating temp. Did you test your fan clutch?

Muddz

The aux. fan should be able to work independent of the A/C, while the A/C is OFF. The PCM should be able to read the CTS and turn ON or OFF the aux. fan at predetermined temperatures, similar to 97-99.

A 01 schematic shows the aux. fan relay is powered through the battery and the pcm controls the power circuit from the ignition by grounding the trigger circuit of the relay.

Battery ------ pos+ --------------|
ST/RUN --- pos+ ----> (radiator fan relay) ----- neg- gnd -----> PCM (radiator fan relay control) closes gnd circuit to power relay.
Fan motor ------------------------|

_____ (from 00-01 FSM)

00-01 XJ - Not Equipped With A/C: The relay is energized when coolant temperature is above 103°C (217°F). It will then de-energize when coolant temperature drops to 98°C (208°F). Equipped With A/C: In addition to using coolant temperatures to control cooling fan operation, a two-gang A/C high pressure switch is also used to control cooling fan operation. When equipped with this high-pressure switch, the cooling fan will not operate each time the A/C clutch is engaged. Refer to Heating and Air Conditioning for additional information.
_____
Description of dual function switch (00-01).

The dual function switch controls the electric cooling fan operation by monitoring refrigerant line pressures. When the discharge line pressure rises above 1900 to 2200 kPa (280 to 320 psi) the fan will turn on. The cooling fan will turn off when the discharge line pressure drops to 1600 kPa (235 psi).

The dual function switch controls the A/C clutch operation by disengaging the clutch when the discharge line pressure rises above 3100 to 3375 kPa (450 to 490 psi). The switch contacts will close and allow A/C clutch engagement when the discharge line pressure drops to 1860 to 2275 kPa (270 to 330 psi).

The Dual Function High Pressure Switch is a factory-calibrated unit. The switch cannot be adjusted or repaired and, if faulty or damaged, it must be replaced.

Testing switch

(1) Disconnect and isolate the battery negative cable.
(2) Unplug the high pressure switch wire harness connector from the switch on the refrigerant system fitting.
(3) On the dual function high pressure switch, check for continuity between terminals C and D. On the two terminal switch, check for continuity between both terminals of the high pressure cut-off switch. There should be continuity. If OK, test and repair the A/C switch sense circuit as required. If not OK, replace the faulty switch.

LOW PRESSURE CYCLING CLUTCH SWITCH

The low pressure cycling clutch switch is located on the top of the accumulator. The switch is screwed onto an accumulator fitting that contains a Schrader type valve, which allows the switch to be serviced without discharging the refrigerant system. The accumulator fitting is equipped with an O-ring to seal the switch connection.

OPERATION
The low pressure cycling clutch switch is connected in series electrically with the high pressure cut-off switch, between ground and the Powertrain Control Module (PCM). The switch contacts open and close causing the PCM to turn the compressor clutch on and off. This regulates the refrigerant system pressure

extrashaky

2001 XJ?

Coolant boiling into the overflow bottle for no good reason?

Am I the only one thinking it?

Turbo X_J

I'll offer $50 sight unseen, OP delivers.

bryweb

0331 Head cracking issues...

cwikk

Tested everything that has to do with a bad head or head gasket, been there done that. It all tests good.

cwikk

I think I'm going to replace the water pump because that's the only thing I haven't done yet, and then I'm probably just going to wire it up to work when I want. I just didn't want to do that unless I had to.

bryweb

Try this Fan clutch, it is for a ZJ but bolts in and works much better. Use P20 code at checkout for 20% off (30% codes might be available if you search), and what tests did you do? Did you check for carbon monoxide in your coolant fluid?

http://shop.advanceautoparts.com/p/c...Term=%23215149