Hi Scotty,
I have a 2011 Ford F450, King Ranch, 4x4, 6.7L Powerstroke Diesel, just turned 100k, and original owner... I recently had my A/C serviced (flushed, checked for leaks, and refilled), because on a trip through Arizona it blew warm air until the outside temperature went below 98 degrees... After the service, it again works fine until the outside temperature reaches about 98 degrees and it starts to have problems cooling even while on the highway... Into the 100+ degree range and it isn't good at all... The force of the air coming out is no problem the air is cool but it just isn't as cold to the point it makes the cabin comfortable... My mechanic who serviced it rechecked the coolant and it is filled correctly with no detected leaks... Yet the hotter it gets the warmer the air it blows... The compressor failed at about 40k miles but that was several years ago... I have had to service the refrigerant over the years but no leak has been found... No other issues to note... What should I do?
It may be that your condenser is not able to shed heat fast enough. Check that all cooling fans are running when the AC is on (including the condenser pusher fan if so equipped), and that the condenser fins are open and not clogged with debris. Condenser temperature should be even across its face, if not then there is a blockage inside.
You mentioned that the original compressor failed and was replaced, was the rest of the AC system (condenser, expansion valve or orifice tube, drier, evaporator) replaced as well? When compressors fail they typically shed metal debris which can lodge in various places in the system so typically all components are replaced. (Parallel-flow components such as condensers and evaporators cannot be successfully flushed out because the flushing compound just routes around blockages.)
