Still noodling with the evaporator temp module.
Went to the yard today and pulled one from a 240D with another manual airbox.
It unplugs from the box pretty easily. Just a rubber grommet sealing it in there. The cord on the other hand is almost impossible to remove without some disassembly that I simply wasn't up to. The takeaway however, is that the module is not rebuildable... the thermistor is encased in plastic like a laminated popsicle stick. Bummer.
So note to future enthusiasts, you'll likely have to snip the cord on the old one. The new one can be re-routed in a much simpler fashion.
I checked the resistance values of the harness that plugs into the AC wheel. Based on the chart Ykobayashi posted in another thread (on replacing thermistors), I seem to be waaaay out of spec.
At 15C ambient, the resistance should be 15.7 +/- 0.5k ohms.
At 25C ambient, the resistance should be 10.0 +/- 0.5k ohms.
I took my measurements at about 22C ambient and recorded a resistance of 18.5... womp womp. So that seems bad.
I had to disassemble the harness to get the probes on something and found a diode (?). Guess this could also be a fail point but I'm out of my depth Donnie.
In the meantime, jumping the switch at the back of the AC dial is providing some pretty sweet vent temps, I suppose how MAX AC should be operating when it's operating.
The bad news, however, is that it essentially turns the AC wheel into a button: MAX.