A/C blowing but not producing cold air

[Pianohawk]

The bentley repair manual says the probable cause of an A/C system not producing cold air is the "A/C compressor is not engaging." The corrective action it states is to "check A/C compressor clutch electrical connector at left of engine compartment." Does anyone know how to do this?

More background. I took my Boxster to get a refrigerant charge and the man doing it said he could not recharge the refrigerant because the "pressure was too high." Any chance I could fix this at home?

thank you,

Colby