[CROWSC]

Although you have pressure at the service port, you may not have enough pressure to trip the low pressure cut out switch, which is usually located on the reeceiver drier. On my '79 the receiver drier is located behind the front drivers side wheel. I would jump this switch with the engine not running and see if the clutch engages. If it does, then you will need to add more refrigerant to the system. In order to get the low pressure switch to close.