No...I have not forgotten about this problem; been living with it everyday still.
Just tonight I installed a reman'ed OEM Motorcraft alternator and the problem persists. Since the car was warmed-up I could get the cooling fan to kick-on pretty frequently by running the A/C. To rule-out the relays in the CCRM (to some degree) I unplugged the fan and ran the A/C again long enough to have the fan commanded on -the engine didn't stumble.
So in spite of previous testing conclusions I plan on replacing the fan. But first I'm going to make sure the wiring to the fan is all good.
More to come and quicker than in 2 years (sheesh).
If this were my car I would be performing a voltage drop test between the fan ground and battery negative on low speed and high speed. Then repeat the test on the power lines and battery positive.
Repeat the voltage drop tests between the alternator case and battery negative as the fan is being cycled. What you are looking for is IF the voltage drop suddenly goes up when the fan draw kicks in. Repeat the measurements between alternator B+ and battery positive.
This should also be cross checked against the voltage at the alternator and battery to confirm that the charging system voltages are stable.
If all of the voltage drop measurements are low, then the only reasonable conclusion left is that the fan is drawing way too much power.
Haven't done the voltage-drop tests yet but I figured-out why the low-speed fan was not coming on. Turns-out the high-current fuse box had been removed. The wires were just cut, folder back, wrapped in electrical tape, and then put back into the plastic harness which had its end wrapped in electrical tape. From what I can tell, this box just holds a 30A fuse that's between the CCRM and the fan motor.
What's on the left side of the picture on the front of the strut tower circled in blue is missing in my car.
So I wired-in a weather-proof fuse holder. The low-speed fan now works as it should. When it runs the engine idle does NOT stumble. High-speed fan still does stumble the idle.
I did end-up getting that ELM327 USB dongle and ForScan. Had some fun with that, especially the bi-directional controls. Wish it could do just a bit more like show live data while activating some of the bi-directional controls. But for the price I'm not complaining -still a geat deal. Thanks for the tip on that.