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.

[mbdoc]

On that car...P1 should be 102 & P2 should be 136.

Set left side to "HI" & right to "LO" , turn off key, hold rest button & turn the key back ON.
Release the rest button & P1 should flash. To store each entry press "EC" for >1 second.

[Robert Squires]

* MBDoc, thanks a million for your help. Since I'm likely to run into this problem again, can you refer me to a reference table of P1 and P2 values for various years and models? Or is it assumed that the tech is going to take these values from the old control unit before he/she replaces it?
* Are these values even stored in the climate control unit, or are they stored somewhere else (in the car)? In WIS? At StarTek?
* If the P1 and P2 values can be read on the face of the control unit, are the values displayed the same way that the real-time ACC metrics are displayed? Thanks again. (hopefully, I'll be able to afford SDS this year and this kind of thing won't be such a hassle).