I need some guidance on where to go next.... My AC works about 50 percent of the time. I had it checked out by a mechanic and he said there are no leaks and everything seems to be running fine from the engine side. He discharged the AC system, and recharged it.

Here are my current systems:

Annoying hissing sound somewhere under the dash. I can't seem to hear it engine side.
The hissing sound ONLY happens when the AC button is engaged.

When the AC is not working, the air is not hot. Just neutral. Turning the **** to the heater side makes very hot air in comparison.

Recirc button seems to work fine.

If I turn AC on/off and/or fiddle with the cold/hot controls the AC gets cold.

I will rip apart the dash if I have to, but I have no clue what I am looking for. I removed the bottom panels and stuck my hand up there and couldn't feel anything. I feel like there is a vaccum leak somewhere but I don't know where to look.

Does anyone have any guidance as to what to do next? Are there any good diagrams online?

It is getting to be in the hundreds here so I want to get this fixed asap but I don't have the money to go to the dealer.

 

The hissing noise is the expansion valve metering the Freon. It should be metering liquid and you would hear nothing. When the system is low on charge, it gets gassy and you hear the hiss. You could also just have a bad expansion valve, do quite a few of those as well. Do you have rear? Does it cool? Usually if you have rear and it cools, full system, bad valve. If you have rear and it is also warm, probably low on charge. Good place to start anyway.