2 weeks ago my 2011 Ford Focus SE started hissing under the dash of the defroster or the AC was turned on.. I took it to a shop and they hooked it up to the vacuum and couldn't find any leaks so they drained and charged the AC system.. There was no more hissing and then 5 days later it started hissing again and the AC started blowing warm air again. What's going on???? I tried to see if it would still be hissing today but it's not hissing and the compressor clutch isn't kicking on but now it sounds like its hissing from the compressor... anyone have any ideas on what's happening.??