My auxiliary fan doesn't run, ever. It got hot enough one time a few weeks ago to kick the fan, the fan didn't turn on. The fan also doesn't come on with the a/c.

2001 Cherokee Classic
What I've done:

• Tested the fan by grounding to battery - It works
• Replaced the big relay in the under hood panel
• Checked the 40amp fuse under the hood for Electric fan - its good
• Checked the 15amp fuse in the kick panel - its good

I haven't replaced the temperature sending unit, but I can't get the fan to come on with the A/C so I figured something else is wrong.

Am I wrong to think that? What am I missing?

 

Have you checked the wiring going to the fan connection?

 

A simple, but effective, way to check the PCM fan relay ground driver, the relay, all fuses, and the fan, is to remove the connector from the CTS then start the engine. The fan should run if all the circuits and components (excluding the CTS) are functional.


You will get a CEL for a P0118 code. It will go away after plugging the CTS connector back in and driving the Heep for 150,000 Miles. ;-)

 

Thanks. I tested in this manner and my fan came on. Not sure why I didn't do this already, but I just assumed since the fan wasn't running when the A/C came on, it had to be something else.

I'll update once I replace the cts

 

Here's data from the 2000 FSM concerning the operation of the cooling fan.

Electric cooling fan 4.0L: With or without A/C request the electric fan will come on only when the coolant temperature is at least 223° F, and will remain on until the coolant temperature drops to 217° F or below. Regardless of coolant temperature, when air conditioning system pressures reach 300 +/- 20 psi) the electric fan will engage and continue to run until the A/C system pressure drops to 235 psi minimum, then the electric fan will shut off.

The 2000/2001 AC system is an odd duck. Read below.

Here's an explanation of the AC Switch functions:





A schematic showing the switch functions: