When the A/C stops all of a sudden, try this: Turn the engine off, remove the key, then restart and see if the A/C works again. If so, your A/C clutch end gap may be out of spec, or the belt may be too loose resulting in slipping. Once the sensor detects slippage, it shuts off power to the compressor until the ignition has been cycled off and back on.

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08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280