Aux fan troubleshooting

[paramax55]

I have an 01 or 02 (manufacture date of 11/01) X5. The aux fan quit working (again). The AC acted like it needed a charge, so I started giving it a squirt, but the pressure didn't look like it was low, so I stopped. Then It quit working a little while later and I thought "I've been through this before. I guess I need to order a new fan." Sure enough, the fan was barely spinning and the high pressure line was hot enough that it burned me like a hot stove.

The fan that was in there was a junkyard unit I frankensteined in from a 4 door 3-something (I don't remember which year/model). The 3-series had a slightly smaller fan, but it was made by Bosch instead of Siemens and the junkyard was full of them - which told me people weren't pulling them to replace failed ones. It worked well for a few years until now.

The new fan arrived, I installed it, and... NOTHING. Damn. If I unplug the high pressure sensor and start the car, the fan will run full speed, so I imagine that the fan itself is OK. Other than that, nothing. I had some spare AC control units, so I tried those to no avail.

I've been looking for wiring diagrams to trace the signal wire from the fan to the DME so I can check for high resistance or even a broken wire. I've found that it's pin "4" but there are multiple connectors and I don't even know which pin is "#1" on each connector. I don't know if there is a secondary signal generator for emergency operation? Something that would let the fan work when the high pressure sensor is unplugged, but not when the AC is on? Or do all signals come from pin 4 on the DME? I'm thinking it's also possible that there is a corrosion/high-resistance spot somewhere that doesn't let the fan "see" the smaller PWM signals from the DME, but the full-on emergency signal is strong enough? I can scope the wire at the fan but, without knowing where the other end of the wire goes, It's really just a pretty picture.

I have an INPA coming, but it won't be here for a couple of days. And I'm pretty sure I'll need to trace this wire back to the DME, anyways.

Does anybody have a picture, or a good description of which DME wire goes to the fan? Barring that, does anybody have any good ideas/information?