A/C blows warm, sounds like there might be a leak in freon lines

needs regas aswith the hissing it has a leak

Sounds like you need to take it in and have the AC checked for a freon leak or low freon, It is what circulates in the air system and keeps the air cold. If it is low or has none it, it it will blow warm air..

It's very common for the EVAP cores to leak on these. It is located in the EVAP housing.

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

YOU NEED TO ADD MORE FREON TO THE UNIT. SOUNDS LIKE IT NEEDS TOPPING OFF. YOU CAN BUY R-134A FREON IN A PACKAGE WITH A HOSE AT A PARTS STORE. DON'T KNOW HOW TO CHARGE THE UNIT , NO PROBLEM. OPEN HOOD, START TRUCK,TURN A/C TO MAX WITH BOTH DOORS OPEN RUNNING AT
NORMAL SPEED, NO REVING, THEN FIND A BLACK METAL PIPE
RUNNING FROM A SILVER DEVICE CALLED AN ACCUMULATOR.
THE PIPE WILL HAVE A CONNECTOR, JUST UNSCREW THE CAP
AND PLACE FREON HOSE WITH THE CAN CONNECTED TO IT AND
SECURE THE END OVER THE PORT VALVE. OPEN FREON VALVE ON THE CAN AND PLACE UPRIGHT AND LET IT SIT. WHILE INSTALLING THE FREON, FEEL THE VENTS BY THE DOORS OR
DASH TO SEE IF THEY ARE GETTING COLDER. WHEN THE VENTS ARE COLD YOU CAN TURN THE VALVE OFF ON THE FREON CAN
AND DISCONNECT IT FROM THE FITTING AND PLACE THE CAP
BACK ON THE VALVE. THAT'S ALL THERE IS TO IT. YOU CAN ASK THE PARTS STORE CLERK WHICH PORT IS FOR CHARGING THE UNIT IF YOUR UNSURE. THEY ALSO SELL R-134A FREON WITH A
SEALANT MIXED IN WITH THE CAN JUST IN CASE YOUR UNIT MAY HAVE A LEAK IN THE SYSTEM. REMEMBER, **NO REVING** NO
MATTER WHAT ANYONE SAYS. THE SYSTEM WILL NOT CHARGE FASTER. IF YOU WANT FASTER CHARGING THEN KEEP THE CAN WARM. FREON WORKS WITH AMBIENT TEMPERATURE WHICH
MEANS WARM DAY OR CAN IS FASTER THAN A COLD DAY AND
A COLD CAN. FREON MOVES FASTER WHEN HEATED.

check to see if compressor is running when it starts getting warm with car running ,if so, see if larger line is cold 

The flap that directs cold air and warm air may be stuck in warm air position. This flap is controlled by a vacuum operated actuator that is attached to the vacuum lines and the control panel. This can go bad. Otherwise check in compressor sight glass to make sure there is no air bubbles or fog, that would indicate a leak in the system

at idle most a/c get warmer as they are not under load to circulate the freon at a rapid pace
changing the dryer is wasting your money won't change anything sounds to me as if there might be a vapour lock in the system. run the car for a week with a/c on max to fully circulate freon to see if the problem goes away if not go back to the shot tell them to check system with gauges on the high and low side to make sure that it infact is properly charged with the right amount and temp.
42-54 degrees is good

you could have a leak in the ac system which would be why you had to add freon. take it to a repair shop and ask them to check fo rleaks because adding more freon wont fix your issue if there is a leak.

problem with blend door either stuck or linkage problem

U have a leak in the system, be it a very slow one. Have the systek leak tested with a black light, it comes from the factory with dye that glows under a black light leak detector.