blacklab

The electric fan in my 99 XJ comes on and off constantly even before the engine warms up.
What controls the fan and can it be replaced.

I've done searches on here and all I get is the fan not working enough.
My engine rarely warms up past halfway on the gauge but seems to me to run hotter, than my 94 XJ did.
Where is the coolant temp unit located on my 99?

CCKen

The Coolant Temperature Sensor is located on the thermostat housing.


Verify the connector is secure, the pins and pin cavities are free from corrosion, and the wiring is not damaged.

michaelo

Usually the fan comes on and off with the a/c compressor which also happens when the a/c control switch is at heating floor AND window.

mikesignal

I would check temperature with an OBD2 scanner or IR thermometer to verify accuracy of the gauge. If you have a discrepancy I would replace the temperature sending unit.

limproved

The first place to check would be the fan relay, which is found under the hood in the power distrubution center. This part can basically stick "on" or "off." If you have factory foglights the relays are the same so you could try simply swapping it out. If that is no go then check the contacts and clean if necessary on the ECT which is the two wired sensor in the thermostat housing. The fan will stay on if this part is unplugged on the 97-01 Cherokees, so a bad connection here would make it run constantly as well.

blacklab

I changed out the thermostat and the temp sensor.
Now runs much cooler and the fan only runs when it is supposed to.
I should have mentioned that the fan was unplugged when I got it from the previous owner.

limproved

Awesome! Crisis averted. My fan was also disconnected from the PO ('96) and mine turned out to be the relay.