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AC blows warm HISSING sound

02-20-2009, 05:16 AM
Hi all,

I have an 02 LS V6. Last summer, my AC went warm. It started with intermittent hissing coming from the dash. When the hissing stopped, air was cold. Hissing present, air is warm. I took it to a repair shop, he "recharged" it, worked "ok" for about month with minimal hissing, and then went warm again and hissing was continuous. Tried to recharge, this time to check for leaks, but system was already full. Since it cooled down, I've neglected trying to troubleshoot, but we get those odd days of high 80s, and I hate having to sweat them out. I'm guessing my DCCV is shot, but would that also cause the hissing when the DATC is in anything but the "OFF" mode? Heat and everything else works fine. Any ideas?


02-20-2009, 12:11 PM
I wonder if the hissing is instead actually one of the electric actuators trying to move. Have you tried the steps to put the control unit in self diagnostic mode and checked for codes? The procedure has been posted in a few different threads and varies slightly by model year apparently.


02-20-2009, 12:35 PM

After I posted that it hisses in anything but "OFF," I came out this morning to do a reality check on that since I rarely use anything other than AC and Defrost. It turns out that it only hisses in those two modes.

I did try two methods for retrieving codes. "OFF+Panel" then "AUTO" It went through the count then all sections illuminated. "OFF+FLOOR" then "AUTO" or "DEFROST" (can't remember exact sequence but I had my note sheet in front of me when I did it), all sections illuminated. I heard the vents cycling each time I performed either one of these functions. There did seem to be a slight clicking sound at some point doing the cycle, but I don't know if that's normal or not.

BTW, the hissing is fairly slow while idling or waiting at a stop light, and speeds up and gets louder as I accelerate.

The sound is similar to when you first switch to "DEFROST" on the climate controller in any other car. You here a short hiss then it sounds like a "flap" closes and hissing goes away. In my case, the hissing doesn't go away. Are there any vacuum components to go bad on the 02?

Thanks again

02-20-2009, 05:43 PM
All of the internal actuators are electric in the LS. Have you tried opening the hood to see if the hiss is more pronounced outside the car, like maybe a compressor bearing is dry? The compressor is actually low on the engine, kind of just to the other side of the driver's lower control arm bushings.


02-21-2009, 09:32 AM
Can you localize the source of the noise? What area of the dash (I assume its coming from the dash) is it from? If you have a faulty actuator or broken mode or blend door that will help isolate the cause. If its an actuator or door problem, its MOST likely to be with the cold air bypass door or actuator (located near the left hand floor duct) or with the defrost door or actuator (can be accessed by removing the instrument cluster). If you can get to where you can access these actuators you can check to see if they are moving or not while you change settings. Of course remember, even if the actuator moves the door could still be stationary due to it being broken ( they are only plastic after all ).

02-21-2009, 09:43 PM
Thanks for the replies!

I checked to see if the hissing was more pronounced under the is not.

It seems to be more noticable from the center are of the dash. Is there a way to tell if I have a broken mode? During the self diagnostic, I did notice a sort of clicking sound replace what I assumed to be the normal sond of the doors opening and closing. The odd sound was noticable for the first five counts (the counting displayed during the diagnostic) or so, then at about five or so before the end. Is this normal, or should the entire process sound only like doors opening and closing? When you (fordtech78) say remove the instrument cluster, do you mean where are the guages are, or just the center portion where the radio and climate controls are? I know that may be a dumb question since "instrument cluster" usually refers speedometer, tach, guages, etc. are located...but I'm hoping we're just talking the center portion only here! :)


02-22-2009, 11:08 AM
When I've run the self diagnostics on my wife's 02 LS I only remember hearing what I'd consider normal door movements, not periodic ticking/clicking. There may have been a relay click or two, but not a cyclic relay click.

You can see most of the actuators from under the dash on the driver's side and passenger side. They are mounted to the sides of the center duct work.


03-11-2017, 07:52 AM
I have this same issue - was there ever any closure on this ?

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