Hi gang,
I have one. The electric fan. My nineteen ninety jeep cherokee is stock with the original and two hundred and eighty thousand miles. I have ran it and everything works. I checked the fan with a wire and I know it works. But I am not electrically inclined and do not know how to use the meter....yet. I replaced every temperature and every other sensor on the jeep. I have ran it in the past and the temp comes up over 200 and it does stop. But CA heat is on and I never have heard nor seen the electric come on (mechanical was replaced, works.). What are some easy ways to check or what should I replace if I have a bad part. Oh, I did replace the radiator with another new stock one.
To add to that, what would be a good (and not over priced way) to upgrade?
Appreciate the input.

 

Take my advice with a grain of salt, I'm just spit balling here. I've been reading other threads on auxiliary fans and here's what I've gathered.
So you have replaced the sensors and sending units, and jumped the fan off to ensure it does work? Make sure the CTS and ECU are working as that's where the auxiliary fan gets the cue to turn on, should be located on the block, near the tstat housing or on the intake manifold. Might be something as simple as a relay or fuse, or even wiring. Then again I may be wrong!

Hope this helps!!!!

 

So just to verify you have a 1990. The electric fan runs under 2 conditions.

1. You turn the AC on. Assuming you have AC and it works, when you slide the HVAC controls to any AC setting or defrost, the compressor will kick in and the fan will come on. If it comes on with the AC, then the fan is ok and the fan relay is OK.

OR

2. The coolant temp gets to about 220-ish (maybe a bit more as indicated on the temp gauge). The radiator has a coolant temp switch located in the radiator tank on the driver side (between the transmission cooler lines. When it reaches temp, the switch closes and turns on the fan. (You did put it back in when you swapped radiators?)

If your cooling system is working properly, it might not get hot enough to turn on the fan.

You can do 2 tests (in addition to the AC test above).

1. Disconnect the radiator switch and, on the main harness side, simply jump the 2 wires in the connector together. Make sure your key is ON, AC is off, you can run the engine too. With the jumper in place, the fan should run.

2. Once you get familiar with the multimeter, set it for "continuity" (resistance testing at lowest range) and then test across the the 2 pins on the switch side. When the coolant is cool, the circuit should read OPEN (Open Loop, or maybe no reading depending on the meter) meaning no connection. If you begin to overheat, (gauge reading above 220-ish or more), the switch should close and you get continuity. This will turn on the fan. Some meters will emit an audible tone when detecting continuity. You can verify the coolant temp by using an IR thermometer at the thermostat housing. Bear in mind that the gauge uses a sensor located at the rear of the cylinder head so it will show a different temp than you see at the housing.

I have an '88. Despite a small leak in my radiator (recently changed too), my fan never came on as my temps rarely exceeded 210-ish on the gauge (rarely even made it to 210). At the thermostat, my IR temp remained about 195-205-ish. Since the temp switch is located on the cooler side of the radiator, the coolant temp there would be much lower.

If none of the above work, look for the little orange box along the driver side inner fender next to the air box. That's a diode that prevents back feeding from the AC side to the Switch side (and vice versa) when one of them has turned on the fan. The diode is circled in yellow in the pic (sorry it's a bit fuzzy). Make sure it's there and connected.