2001 Honda CR-V A/C will blow cool for 15-30 min then go warm?

My 2001 Honda CR-V has 170,000 miles and it blows fairly cold air for the first 15-30 minutes but then gets warm until I let the car sit for a few hours. I have not checked the cabin filter yet since on this series of CR-V it is the hardest one I have had to get to, so wanted to ask first. Do you think it is that? Also, it doesn't sound like the compressor turns on or off if that makes a difference.

First you need to make sure the compressor even runs at all.Start the car and turn the ac on max. If it doesn't come on, check the fuse and relays.A bad relay, low freon level, defective ac clutch cycling pressure switch, faulty compressor, or open or short in wiring to compressor will all cause the compressor to not function. Make sure both cooling fans come on when you turn the ac on. If the condenser cooling fan doesn't come on when actuating the ac, that will cause the ac to start blowing warm air after 10-15 minutes. When freon leaves the compressor, its in a hot high pressure vapor state then it goes into the condenser(in front of radiator)Once its in the condenser, the cooling fan pulls the heat from the freon which makes it change state to a warm high pressure liquid. If the fan isn't working, freon won't change its state, so the ac will only blow warm air.Another thing is evap core freezeup.Anytime the ac is on max, the blower fan needs to be set on the highest or next to highest level