[arucano]

If the system pressure is too low, the compressor will not engage. It could also be a faulty pressure sensor. If the gas pressure is high enough for the compressor to kick in. Test the compressor clutch resistance for continuity. If that is OK, the problem is in the control system for the clutch (I think there is a relay in the circuit).
If someone on the forum has a diagram, it would be handy if it could be posted so the diagnostic steps can be worked out.