front A/C slows cooling

Just drove 4500 miles with travel trailer. Notice front A?C blows less and not cold air while rear is fine. After the engine cools it works again for a while but the same happens. A/C never been worked on. Could it be simple/cheap for achange? Maybe just freon, any suggestions? Also engine idle changes when cooling lessens. It appears to fluctuate. Runs smoother with A/C off

Have you ever changed the cabin air filter? I assume this is for your 2001 Sub, right? It does have a cabin air filter.

//2000CAYukon

I do not think my 2001 has air filter in cabin. However story continues. Had it checked and found that heater coil was bad. Was replaced and no longer is there leaking of coolant and engine does not 'ramp rpm's". However a week later the ac still does not cool. Went back and was told it was just a valve on top and needed evac/recharge. Later in the week it stopped cooling (actually never cooled right) when stopping at stoplight. It would slowly stop cooling and blow ambient air. Took it back again and now they replace oraface tube, evac/drier and recharged......now it does not cool at all any more....!!!!!!!!!!!!!!!!!!! Went back again and was told compressor does not engage?? AM I BEING RIPPED OFF?? Will go back today to talk to manager. Seems that one partfailure has let to the next failure etc.
ANY SUGGESTIONS. PS High side was 275 and low was 32-35 according to the mechanic, indicating a blockage which supposedly was the oraface tube BUT IT DID NOT FIX AC. HELP.

Something seems wrong. If the compressor did not enguage you would not have those pressures. both sides would be the same about 60. Feel the inlet pipe to the evaporator with the A/C running. It should be about 35-40 f. and sweating. I think I would find another repair shop.

Went to shop yesterday and was told the dropball inthe line is stuck, blocking the freon. That is why compressor does not engage. Sounds right? Dropping it off again today to get whole line replaced. I know it did not sweat and was hot. Isn't this where the orafice tube also is located? They just did replace it. Must have been a bad dropball valve, whatever it may be. I will keep you posted. Thanks for the answers......

Update: after being in shop again and replaced the lines with orifice tube it seemed to work well, until next day when it only worked on/off. Blower would blow but warm air. Compressor would not engage due to low pressure switch malfunction. Was replaced yesterday, SO FAR SO GOOD!!