Air conditioning problems after engine replacement

I have just replaced my engine in my 1997 Blazer. The engine is a 4.3L. The air conditioning worked fine, before the engine was pulled out. But now it's only blowing in outside air. There is no difference in the vent or a/c selection. I didn't break any of the refrigerant lines. Both electrical connectors are connected to the compressor, and I'm not able to see or hear any vacuum leaks. My a/c fuse is good. The Serpentine belt is spinning the compressor, and the compressor is making no noise. When I turn the a/c on, I never hear or feel the compressor kick on. Could I have missed a wire, vacuum line, or could a relay gone bad?

Thanks,
Chad

Well very well could have miss a wire hook up somewhere. And vents will be affected if vacuum line left un hooked also. If vaccum line left off vents will blow only floor and defrost.

Well very well could have miss a wire hook up somewhere. And vents will be affected if vacuum line left un hooked also. If vaccum line left off vents will blow only floor and defrost. Just run 12 volts to the compressor and see if it kicks in if not you missed somthing in the wiring. or the system leaked do you have a pressure gauge?

I don't have a gauge set yet? I have never had air conditioner problems before, so I'm going to have to get some gauges.

to check the compressor take the low pressure switch off the accumulator and jump the two terminals on the pigtail while the engine is running and the ac on with the blower on full...you should hear and see a the clutch engage on the compressor...remember this step if your compressor checks out and you refill the system yourself...the compessor MUST be running in order to add 134a (refrigerant), also note the low side is the larger line...the compressor will not run is the refrigerant is too low...good luck