1995 Blazer - No A/C, vacuum leak?

I have a 1995 Blazer and the air conditioning is not working. When the control switch is set to any of the A/C settings (Max, Normal, Bi-level), the air flow (warm outside air) starts at the defroster vent (near windshield) and then eventually begins to blow air from the correct vents. The air flow also changes while driving, switching between fast and slow air flow. I can hear what sounds like an air leak when inside the vehicle. There is no power going to the compressor with any of these A/C selections. Any help would be greatly appreciated.

Jim

Need engine size and AT or MT transmission and VCM or PCM computer.

The controls use vacuum and electrical switching.
If there is a vacuum leak or hissing try to locate it.

Always check for good vacuum from engine threw vacuum tank to heater controls.
Lot of plastic vacuum line that break or crack or come unplugged.

Does the tempt change any from cold to hot?

If no ac compressor clutch on check fuse and check system for proper ac charge.
Low charge and the compressor will not turn on.
Get a low and high side gauge set and with compressor running or jumped to run post back low and high side gauge readings at idle and at 2 K rpm.

It's the Vortec 4.3, AT, not sure about VCM or PCM. Is it possible that the vacuum leak has something to do with the lack of power to the A/C compressor? Or are these two separate problems?

Could these be symptoms of a faulty A/C vacuum control valve?

And the temp will change from ambient temperature on the cold dial setting to hot air when switching the temperature dial to warm.

I will check the vacuum lines in the engine compartment.

Thanks,
Jim

Compresser uses electric controls.
Vents us vacuum switching.
On no compresser clutch on check fuse and ac R-134a charge.
Get the gauges on it and jump compresser and post back low and high side readings at idle and at 2K rpm.
post back readings .
Then we can go from there.

Ok I will try to find the vacuum leak and then look into the refrigerant charge.

Thanks.