ac problem on 95 s-10 blazer 4dr

last year i replaced the ac compressor because it broke down, took it to get recharged. it throws cold air or at least cool sometimes. my main problem is that when i turn the knob to ac the compressor does not engage i would have to push the clucth in the compressor or give it a good high rev to engage but as soon as i start to drive the compressor shuts off to restart it i would have to do the same again. also for some reason only my 3&4 fan setting work not my 1&2 in either in hot or cold air settings.

For the fan you have a bad resistor, for the AC you sound like either you got a bum compressor or pressure is still to low.

how do i fix the bad resistor to make the fan work

Pull the fan motor casing, it's on the harness just inside the box.