Cooling fans always on

[halcyon]

well then, we will try this way, found this last night and now have a clearer picture here is a diagram showing the link between ecu and fans . ECU ports ACS85 grounds the A/C relay and FANH A12 grounds both the A/C relay directly and the cooling fan (radiator switch on the diagram) indirectly through the Timer. So I think that the dblue wire from the timer (or to the timer) that i cut is linked to port ACS85 and when I cut it broke the ground to th A/C relay and that fan shut down. So armed with this new info I believe that it is either the ECU at fault or possibly the heater A/C control in dash that is signaling the ECU......holy smokes, is this ever a complicated way to run a fan...Now that I have a clearer picture of this and a freshly charged battery in the ohm meter lets see if we cant narrow this down....

[oyajicool]

Then, it is as good as trouble solved.

[halcyon]

here is another schematic showing a diode in the mix http://repairguide.autozone.com/znet...528005fa2d.gif
well, after disconnecting the ecu the fan timer, the heater control panel, both thermoswitches, the A/C relay and the cooling fan relay the blue wire that grounds everything is still going to ground somehow
As this circuit runs from the ECU to the heater panel to the fan timer through the firewall and to the underhood fuse panel and also up to the A/c relays short of replacing the whole harness gonna be tough to find the cause. maybe the diode btween the condensor fan relay and the heater panel switch?

[halcyon]

Finally,....solved the problem. After taking the dash apart, to trace wiring from fan timer to the ecu via the heater panel could find no visible issues with the harness. So to be sure I cut the bue wires (ground) at each component in the cabin and still the wires were going to ground. So next I went under the hood. Followed the same procedure to all components and still had the same results. At this point I decided to install a completely new, simple circuit to run the cooling fans using new relays etc and the existing switches which I already had tested and confirmed good. 30 minutes later I had it all wired up,tuned the key on and bamm, on come the fans . OK, I said to myself, the only thing old is the green plug to the thermo switch. so I cut the plug out, tested with the ohm meter and ......proceeded to dismantle #%@^& plug cleaned the dielectric crud out and discovered that someone (as in not me) most probably using a test light, had mangled the crimp portions of the pins and they where in contact with each other. A poke with probe and a little dab of silicon and good as new, problerm solved. 2 hours of reassembling the interior and returning the underhood to stock and now back to the previous owners complaint of intermittant temperature spikes at idle . So now onto replacing the thermostat and, fingers crossed that will be an easy fix.
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