version coding

[Robert Squires]

* My question is about version coding a replacement climate control unit (in a 2000 E320). This can be done without the HHT or SDS, by using the buttons on the face of the climate control unit.
* After rereading the coding instructions many times I still don't see how to arrive at the P1 and P2 values which are to be programmed into the unit. Where do I find the values that sum to P1 and P2? I have a guess, but would rather understand this and not just experiment on the car.
* To possibly make matters worse, the climate control unit in the car now not only isn't the original unit, it's also not the correct part number (it's a 140 unit, and without the charcoal filter switch).
* After the original climate control switch was replaced (with the incorrect unit) the EC light stays on (when the ignition is on, w/ or w/o the engine running) and the AC won't come on.