I would begin by looking at the wiring at the compressor connection, the wires have a tendency to break at the sloder joints. Give a good tug on the wires, you'll know if they need to be repaired.
Use a jumper lead and jump the clutch with a direct voltage, should engage.
If the clutch engages, use a Multi-Meter and check the voltage output of the speed sensor. >300mV AC
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