The A/C pushbutton sends a signal to the BASE module...that base module turns the compressor on.

If the compressor never comes on, possibly that base module has a code to BLOCK the a/c operation.

A good MB scanner can read codes & LOOK at "live" data to see if the command from the pushbutton control is ACTIVE.

Have you disconnected the wiring at the compressor & yank on those wires? they do break there.

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