I have 2011 Expedition EL Limited and ac is driving me crazy. It is making hissing noise in front behind dash close to glove box. Noise is louder when idling and goes down as I accelerate. There is also hissing noise in back too when rear ac is on. Noise is only there when ac is on. Also when I switch rear ac from cold to hot it stops blowing in rear wents but front is fine. Seems like my ac is colder when i accelerate then when I idle . Any suggestions? Took it to mechanic and he said looks like my compressor is dying. On 2011 for real :-( and also he said for rear that door is working but we still cant figure out what it now blowing any air when swithced to warm.