Thanks for the replys.
I found the two fan relays, where suggested. The green one in the middle right hand slot has a 30A fuse and I believe this runs the fan at full speed when the temp sensor on the thermostat housing tell it to.
The other, behind it, is blue and had a 15A fuse which had blown. I carefully opened up both relays and they looked as good as new inside.
I replaced the blown fuse(15A) and.....bingo....the fans started working turning slowly after the A/C had been on for a minute or so.
However, they stopped working the next day and I found the fuse had again blown.
My rudimentary knowledge of electricity made me query why, if the two fans drew 30A in one operating case and it is the start-up surge that blows the fuse, why only 15A on the A/C relay I think the previous owner may have fitted the wrong fuse.
The handbook and manual are no help here. It would have been very useful if MB (or whoever) had printed the fuse rating on the relay, along with all the other numbers and makers codes.
Anyway, I've upped the fuse to 30A and it has worked okay since.
Next payday, I'm investing in new MB antifreeze, and will thoroughly flush out the system first. Anyone have knowledge of "Febi" antifreeze which my local independent tells me is to MB spec - but less tha half the price!
Fingers crossed that the uprated fuse fixes the problem!!!