my ecu is making a weird hissing noise whenever i turn on my AC...At first, i thought it was my speaker but i turned off the radio and its not the speaker....and my AC isnt blowing really cold air anymore, just kinda cool but not cold like its suppose to be... Any ideas on why the ecu makes that hissing noise ONLY when the AC is on? Or maybe its not the ecu... but it sounds like its coming from there...

 

probably a high pressure line or condenser on the other side of the firewall.

I don't think your ecu can make any noise. lol