[mpumas]

No freon in system, leak in freon piping, blown fuse (no.7) 7.5A, bad ATU. Does the compressor clutch engage? If it is out of freon, the clutch won't engage. You can check system pressure by hooking a guage to either the inlet or outlet fittings. You can short the pressure switch and see if the clutch engages with A/C selected. I think the system uses R-12 unless somebody converted the system to R-134. You can check by looking at the low/high pressure inlet fittings.