One morning I went to start up my car and the battery was dead. I change the battery out and I started up the truck, it ran for a few minutes and then cut off. I drove the car and when I would come to a stop the engine died. The next day I drove the car and the engine did not die, but when you turn on the air condition the rpm would fluctuate and once you come to a stop the car would die.
The way you are describing the driving condition it sounds like the engine is running poorly and not the A/C system itself.
Checking the condition of the charging system should also be done to find out why the battery went dead. If the truck is not charging and you use some accessories like the A/C, this will drain the battery and will not have enough current to run the ignition system and cause the car to stall and have trouble starting.
First we need more specific information on your truck like the year, make, model, engine size and if there is a check engine light on. If a check engine light is on then the system should be scanned for any codes, then have them repaired first before we can go any further.
Giving us this information can help us help you better.
Let us know how you make out. Get back to us when you can.