The Klima provides two functions on a diesel:

1) it compares the rpm of the engine (from the crank sensor via enine electronics) to the rpm of the compressor (from the speed sensor on the back of the compressor) This is to save you from being disabled by a torn belt. Workaround: toss a spare belt into the trunk.

2) For some unknowable reason, it controls power to the kickdown relay.

So thats what it does, and now you can assess the risk of bypassing it.