Creating this thread for my brother who has a 96 Taurus. He says the car has cold a/c air for about 10-15 minutes and then the cold air goes away. After that, it only blows warm air. If the car cools down, the same symptoms will occur.
The car does sit for months at a time. Sounds to me it is an a/c coolant issue. If it was a leak, wouldn't it eventually all leak out and then there wouldn't be any cold air? I am heading down to his house in few weeks to look at it. Any suggestions from anyone before I get there would be helpful.

It could be slightly low on refridgerant and the A/C evaporator core is freezing up. However, I would expect that the air flow from the HVAC vents would be reduced at the same time.

You could have a faulty compressor clutch that opens after it heats up. Can you describe to your brother how to check for clutch engagement, and have it check it when the air starts blowing warm?

When the cold air stops, is the warm air just warm, or is it hot like the heater is on? Does anything change if he selects "Max" rather than "Normal?" Maybe there is a vacuum leak in the HVAC system and some vacuum servos are changing positions.

Does his Taurus have the Electronic Automatic Temperature Control (EATC) or manual HVAC controls? If EATC, you can have your brother put it in diagnostic mode and check for faults.

-Rod