Low Speed Fan problems

Ah, I've been doing some research on all this.

THe EDF control is some sort of solid state electronic gizmo that I'm having issues finding info on. Simply stated, there is a safeguard in the cooling system - if the ECT circuit is open, the fan comes on (you dont even need the computer to have power for his to occur). So the default is for the fan to be ON - the computer interupts the pathway to shut it off. I have had issues finding info about what it takes to simulate what the computer does to turn the fan on (does the computer ground or apply 12 volts). Some of this involves the EDF control, which I cant deduce how it works since it's solid state.

This diagram shows a bit of the circuit.

Here is the same circuitry shown a little bit differently.

I also would start at the CCRM and work backwards (the PCM and EDF control relay are two things we cant troubleshoot effectively, so I start at the fan and work to the CCRM, and so on).

As you said, if you have 12 volts at Pin 14 at ~208*F or above, but low speed doesnt come on, that suggests a CCRM issue (or that low speed on the fan or the wiring from the CCRM to the fan took a dump). Oh, you would want the aligator clip on your test light connected to ground (because 12 volts it put through Pin 14, you need ground on the other end of the light to illuminate it).

I'm not one to open up a CCRM - I hate small stuff like that. Here is a picture of the CCRM opened up. I would simply do an external relay instead. You could do so without cutting wires (do Y-solder joints). Or do it right and get a www.DcControl.com unit. I just ordered mine from Brian earlier this week (it's something I've wanted for a long time, though I could have fixed my existing set up - I never liked manual fan switches and all that). I'm very excited to install his controller.


That's what I got for now. Lemme know whatcha think.

Good luck.