I have a 2004 f 150 lariat and my AC doesnt work I turn it on and it shuts off and keeps doing that any ideas

It sounds like you may be low on Freon or have a bad lowpressure switch. The outside temperature can sometimes affect when the A/C will work. If it is near freezing outside, the A/C may not stay on constant, just cycle.

You can switch the lowpressure switch easily without losing Freon. If changing the switch does not help, you need to add Freon. It is best to check for leaks and you really do not know how long the new Freon will take to leak out. Your truck is 6 years old and only needs Freon now. What you add can last another 6 years or 6 minutes depending on the leak.

There are gauges you can borrow from Autozone or Oreillys or a number of independent stores and they are called Manifold gauges. There are also products with leak detectors and stopleak that you add through the Freon fittings. You can do some of the work with the fittings on the new cans and eliminate the gauges, it depends on what you buy.

I would replace the lowpressure switch and see what happens. Then add a can of Freon with stopleak and see how long that lasts you. At some point you will need to determine how much pressure is in the system(how full) and top it off.