I have a 2008 f-150 stx 4.6, My ac is not cooling at all but the compressor work when the ac is turned on at full blast the compressor starts to kick on for a couple of seconds then turns off for about five seconds I have a vacuum pump and a gauge set for the ac system, I have emptied the whole system and recharged it afterwards it got a little bit colder but not for long then I added some uv dye into it and looked around for any sign of a leak but couldn’t find one..........


any ideas?

 

From your description it sure sounds like you have a leak. I had similar problems recently and while I was laying underneath I found uv dye on the bottom of the compressor and decided it must have been leaking from the compressor housing itself. I could only see this whole laying under the truck. Mine is an 04 5.4 so you can see it from above really.
You could try to take a shim out of your clutch, but it sounds more like a leak than a week clutch.

 

use your vacuum pump... pull vacuum on it and see if it holds.

 

Check the two lines going into the evaporator, they should be cold when the compressor is running.If you emptied the system, I hope you connected a vacuum pump to purge the system of air prior to refilling.If there's air in the system, it won't work efficiently at all.