Electric fan not turnng on until 230!

[4Pawprints]

Hi. I'm new to the forum and I'm having a fit trying to get this heating problem resolved. I have a 1994 Cherokee 4.0L. I was having a severe heating up problem and have so far changed the water pump, radiator (put in new 3 core), thermostat, heat sensor (the one in the thermo housing), the overflow tank and the electric fan relay. Short of taking all the hoses off and replacing them, I can't for the life of me figure out what is going on. The new radiator and thermo work great, but at the point that the coolant isn't cooling off enough from the clutch fan, the electric fan doesn't kick in to help. The gauge hits about 230 before it kicks in and it kicks off at about 210. I was told it should kick in WAY before that. Any thoughts?

 

[Sly8795]

I'm not sure if its the same on your jeep as mine is a 90 and has different sensors. But I think your jeep has a temperature sensor. I would look at that. I replaced everything like you did and it came down to a damn $10 part. If it is that your fan might be turning on at the right time and off.

 

[TerryMason]

Bad Cherokee fan clutch

Found this after a little research - hope it helps

It could be a bad fan clutch. To check the clutch fan, disconnect the bi-metal spring and rotate it 90° counterclockwise. This disables the temperature-controlled, free-wheeling feature and the clutch performs like a conventional fan. If this cures the overheating condition, replace the clutch fan.


How to change the fan clutch
The fan and clutch are fastened to a pulley with a large size hex nut which you will see directly behind the fan (toward the back of the vehicle).
You need to get a wrench on that nut and loosen it counter-clockwise while keeping the pulley still. Most mechanics have a special tool that allows them to do this.

 

[SteelHeadz]

AUXILIARY ELECTRIC COOLING FAN
Models equipped with a 4.0L 6-cylinder engine may also have an auxiliary electrical cooling fan. This is with models that have air conditioning and/or heavy duty cooling. The fan is controlled by the cooling fan relay, which is located in the power distribution center (PDC) Power Distribution Center (PDC) For the location of relay within the PDC, refer to the label on PDC cover.

When coolant temperature reaches approximately 103°C (218°F), or when air conditioning is requested, the powertrain control module (PCM) provides a ground path for the fan relay. This ground is provided to the cooling fan relay through pin C2 of PCM connector C3. Battery voltage is then applied to the fan through the relay. When coolant temperature drops below approximately 98°C (209°F), the PCM opens the ground path to the relay. This will prevent the cooling fan from being energized.

 

[TerryMason]

Hmm, Mikey's answer seems much more likely than mine

 

[SteelHeadz]

MMMMmm. i dunno Mr. Mason. i just wanna share the electrical part of the cooling cause you've covered the mechanical Part of it already. so now it's all up to Tracy to do the Homework. i just hope i'm contributing on some help.

 

[Dirk]

Steelheadz hit on it.

Just turn on the A/C. It will override the temp sensor signal and turn on the aux fan.

A lot of guys think that turning on the AC when the jeep is already overheating will only make the problem worse. Not so on an XJ- as long as everything else is working properly, your temps should come down...8)

The circuit that turns the aux fan on without the AC always seems to come on way too late.

 

[4Pawprints]

Thanks for your help guys. I really wasn't expecting it to turn so cold here so quickly so now I guess I'll have to wait til Spring to see how well it works!

 

[Dirk]

Thanks for your help guys. I really wasn't expecting it to turn so cold here so quickly so now I guess I'll have to wait til Spring to see how well it works!

Run the defroster in the winter.
That also overrides the temp sensor circuit and makes the aux fan come on.

An XJ can run hot in somewhat cold weather too, since the aux fan covers 50% of the radiators cooling area.