Measuring AC Compressor Clutch Gap

[deanyel]

I've done a search but dont' get it - how do you measure the compressor clutch gap? Can it be done on the car or does the compressor have to come off? Or does the serp belt have to come off? I just don't see a place to measure. Car is a 400E, MB compressor part # 000 230 06 11 80, which I believe is a factory rebuilt Nippondenso. I'm getting a compressor clutch blocked fault code and this seems to be a good suspect. Any help appreciated.