Here it goes. I had the problem for months. The coolant fan starts
running when the acc. power is on. So, basically the fan running
all the time when the car is started. It's a G2 auto, 91.
I changed the thermo switch, i change the fan timer unit under
the dash. I checked the relay. All functions ok.
The weird thing is if i reset the ECU, the fan will function properly
for a cycle or two. Then, start to behave the same way.
If i check the manual there is a diode plug in device. I would like to
check that, but where is that diode block located ? anyone knows?
and any other ideas? please. Could it be my ECU?
Thanks,

 

I don't think I can help, but if you can't get it working, you can do what I did and just wire it up to a switch on the dash. Actually, my condenser fan is the one wired and the coolant fan is not functioning. Never had any overheating problems even with the smaller fan. Just keep an eye on the temp. gauge.

Greg