<< that the plug where the aux. fan harness from the fusebox and the harness from the fans plug together (right next to the receiver-drier) has either a bad connection or a bad wire (this was the real problem), and
3) something is stilly fishy with the drop resistor and coolant temperature sensor.
Here's the issue: when I bypass the drop resistor, BOTH fans will work when I jump the a/c pressure switch. They both work whether the coolant temp switch is connected or not. This seems strange>>
Nothing strange there , that is Normal
You have some conflicting info here, but I will try to expalin the basics
The Resistor is to lower the voltage to the fans when the a/c pressure sw is activated by a/c high side pressure or jumpered..
If you jumper the resistor AND the a/c pressure sw, you will have HIGH fan [ both fans, at high speed ].. If you then remove the resistor jumper , you will have LOW fan [ b/c the resistor is now in the circuit and dropping the voltage to the fans]... if you now have no fan , you have a BAD resistor/connection at resistor...
Do not confuse the resistor circuit with engine coolant sensor circuit ,, these two circuits have NOTHING to do with one another .. they only SHARE the same fan motors at the end of each circuit.
The ECT circuit is HIGH fan ONLY, and does not use the RESISTOR..or, for that matter, the a/c sw or relay..
The fans are wired in Parellel, so they work in unison... if you see some bad wiring at the connector that you mentioned , it is possible you have incorrect wiring there and even possible series hook-up..
It is hard to visualize these two circuits , but if you could see a schematic, you would plainly see how the two feeds come to the common fan motors..
Do you have a schematic, by chance??
Email me offline and I can walk you through it..