Have 02 Lariat SCrew with the Climate Controls (not switches) which means I do not have a fan resistor like I have been reading. I have a unit on the passenger side kick panel instead that the wires pass through before they get to the fan. 3 wires in- two wires out. Fan stopped working without notice (no other events I know of happened at the same time except for turn signal fuse which makes me highly suspicious because the relays are side by side underneath the dash which I found thanks to this forum). Exchanged it with new one from parts store--got nothin. Thought that might be bad so I exchanged it with one from position #4 on inside fuse box--nothin. Just as a test, I used the Blower Motor relay to test the "one touch window" (position #4). That relay worked in that position. On one thread it told me how to diagnose EATC--did that--no error code. (By the way, a lot of posts say to press the "off" and "defrost" button simultaneously. On my truck--after trial and error, only pushing "off" and "vent" did the test actually commence) Moving on--No power to the wires before or after the "blower control unit" (the glorified resistor). Fuses checked--all good. I would check the wires at the relay but that is pretty much impossible due to the confined space. Am I missing something here?

One thing--and I know its a formality--but even though there is no power to the wires at the fan, I would like to wire the fan directly to the battery to at least hear it run, but nowhere on the forums have I found how to do that. Are the two wires supposed to be hot and one just varies in voltage and the fan grounds itself internally? Or is one wire (-) and one (+)?

I must have read 40 threads about my problem. Only problem is, the usual fixes are things I have already checked. What else is there?

 

The fan speed controller is a solidstate device that is continiously able to control the fan to any speed, unlike resistors that only offer fixed speed levels.
The center offers a signal to the fan controller to vary the speed.
If you have voltage into the controller, it does not feel warm or hot but none out, replace the controller same as you would in a resistor system.
What the fan controller is is a 'high power' pass regulator controlled by a low voltage input from the center. The fan takes a lot of current on high speed setting so the speed controller dissapates a lot of heat dropping the voltage and current accross it.
This is close to the same system used way back in the late 80s in the Lincolns.

Good luck.

 

Figured that, although, there is no voltage going in or out of the controller. I would assume the last stop voltage would come from would be the relay?