Re: AC Compressor not kicking in
The wire referred to runs to the compressor clutch. It feeds current to the clutch coil located at front of compressor when engaged. If the disc at front of compressor pulley is not spinning when engine is running and A/C is switched on, then no power is getting to the clutch. There is a Hi/Low pressure switch in the system to prevent operation in either condition, if this has tripped, then it interrupts power to the clutch. If you wanted to test the clutch operation, you could manually feed 12VDC to the clutch wire past the hi/lo switch, just to see if it operates, and to eliminate it from the hunt.
Does blower inside car have to be on for AC to run ?
Could be faulty pressure switch, or as suggested, a small leak in system - usually in rubber portion of hoses or at their crimped connections with aluminium pipework. R-134a is a tiny molecule, even smaller than R-12, so it can find the smallest holes in the system, and rubber hoses will perish over time. Could also be a blockage in the system at capiliary tube near evaporator - these are tiny bore tubes, and if molecular sieve has broken down internally, it can release small particles of dessicant, which block the cap tubes and trigger the pressure switch. There are leak detection kits available for DIY, but specialists would have the correct gages and manifolds, leak detection dyes, and sniffers to find leaks - plus they know high side from low side in the system. Best left to them, I think !