Well I held off as long as I could, but I need some clues, here's the basic story:

84 Euro 280CE with basic HVAC like a US 240D, not Climate Control.

Just had a hose replaced after it leaked last year, so the A/C been out for a few months. The problem now though is with the compressor clutch.

With the key on, but the engine not running, the clutch will click on and off when you turn the switch, however once you start the engine, the compresser will not engage until you turn off the A/C and then turn it on again. After this initial start the A/C will cycle all day long untill you shut off the engine, then you have to go through the same proceedure after you restart the engine.

My guess is to do with the draw of the starter while cranking, but where should I go from there?.

PS maybe it's time for a dedicated A/C forum, next to spark plugs and synthetic oils LOL

The SOHC 103's have a speed sensor that detects a loose serpentine belt. If so, the a/c is shut off. One has to turn off the engine and restart in order to reactivate the a/c.

I wonder if your system operates in a similar manner?

I had thought about that, but since I dont have the serpentine belt, I discounted it. I think it has to do more with the draw during the starting cycle and either a duff relay or resistance in the feed to the clutch, but I don't know which. I have tried new relays in the spot on the fender, but I wondered if there was another I can't see.