Air con failure

Hi

I have just paid for my aircon to be checked out because it failed on a warm humid M25 last week.

The garage says the electrics are fine the computer diagnostics say everything is fine the light on the dash says its fine. However the clutch mechanism on the compressor shaft appears to have melted plastic extruded from it and the shaft does not rotate.

Has anyone else experienced this si****ion if so what is the cure?

Argus