My aux fans are not coming on at all. I did use a decade box and was able to get them to turn on in high speed only. There is a black tube style resistor that is located in the front of the aux fans that, from what I have been reading is junk. Most sites suggest removing that resistor and installing the old pre-1994 resistors in its place to correct this issue. There seems to be alot of information but nothing solid on how to wire the resistors in place. The two speed fans is pretty simple and clear cut. But every picture I find of the 3 speed fan wiring has words written in the place that shows the wiring.
https://www.k6jrf.com/R15_R151_dwg1.gif . Every place has the exact same drawing - including my All Data Maintenance Manual. The R15 is right over where the wiring is running.