AFTER DRIVING MY 2003 V70 ON THE HIGHWAY FOR A LONG TRIP THE A/C STARTS BLOWING WARM AIR. I THINK IT MAY BE THE EVAPORATOR TEMP SENSOR FAILURE, HAS ANY ONE ELSE ENCOUNTERED THIS?

 

That is very possible Ive seen this many times before.It could also be a bad compressor when it gets hot it will shut of then when it cools down it comes back on.If the evap. temp sensor goes bad then usualy it will freeze up when it happens open the hood and try to see if the lines are frozen.