Budget computer control for electric fan doesn't work

The title says it all: Budget computer control for electric fan doesn't work.

I tried it with an A9L & A9P computer, and it didn't work with either one. The tech note from FordFuelInjection.com, http://fordfuelinjection.com/files/A9L_E-Fan_How-to.pdf said that it worked for some but not for others. I think the number of computers it works with may be very small. I have no way of knowing what works and what doesn't other than doing their test proceedure.

I guess I'll save my $$$ for a DCControl fan controller.

Keep in mind that the computer outputs sink current (provide a ground) rather than source current. This prevents damage should the computer side wiring short to ground.

How I tested this circuit to see if it works: Since pin 41 is supposed to go to ground when the temp rises above a certain point, I did a simple test. What I did was to use a 2K ohm resistor in series with a LED. The resistor side of the LED went to pin 41 and the other side of the LED went to 12 volts. The result was that the LED was on anytime the ignition switch was on, no matter what the engine temp. What I was looking for was the LED to be off when the engine was cold and on when it was warm.

I went through the ECCTuning site and didn't find anything more than what I already knew. Some computers work, some don't. The LED test is a simple way to find it it works or not.