Ok, I'm taking ONE last stab at my cooling system before I give up and buy a ton of dry ice and a truck mounted freezer. So far to fix my overheating problem I first wired up a toggle switch for the fan since I had wanted to put one in for over 2 years and was never given proper motivation (slight steam burns motived me). Switch works fine, fan turns on now even when hot. Here's a run down of what I've down and my theories for eliminating potential malfunctions.

I swapped out the stat for a Robert Shaw 180* one.
Determined the motor did not have enough umph to turn itself over anymore, replaced the motor, runs like a champ when I use my switch.

I personally did not test drive it after the fan motor swap, but my father tells me it heated all the up to the red and did not turn on. On the bright side, he flipped the switch and he said it cooled off really quick. so... my switch is run from about an inch and a half off the ecm, wouldn't that eliminate the wiring to the relay, and the fan motor? Is there anything else between the ecm and the fan relay on an '86 LB9? It's a single fan setup... or am I buying a new ecm next week?

 

Not sure but it sounds to me like it's your switch that's keeping the computer from turning the fan on. Running the wiring so that it turns on either way is a little more complicated. But having said that I haven't seen how you wired it so you may be way ahead of me. If not I'd run a jumper across the switch and warm up the engine and see if the fan comes on.

 

I could tell you how I wired the switch if it'd help. There are three connectors on the back of the switch (it's a light rocker)

Acessory on - Wired to the drk green/white wire off the ecm
Supply vots - wired to ground
Ground - wired to ignition on 12v

I know it's a little backwards for the ground connections but the LED in the switch comes on and so does my fan.