This system is very simple mechanically and it doesn't sound like an electrical issue at first glance. I would point at the expansion valve but I'm not sure. There is not much to that valve. If you have an over pressure condition it would seem the compressor is doing its job. If you go to VW and ask them for an Etka view of the system they will give it to you. However it will only show you the engine side of things, ask them also for the Evaporator components, that will get you the rest of the physical system drawings.