Hissing sound inside dash
Safety Car
Joined: Oct 2000
Posts: 4,949
Likes: 10
From: Monticello MN
Interesting. I've got a hiss if the unit is off, or if air is directed just to the floor or to the floor and the dash outlets. If directed to just the dash outlets, there is no hiss. Don't know where to look. I know the dealer is going to want an arm and a leg to find it. 
Ed
Ed
Instructor
Joined: Apr 2011
Posts: 196
Likes: 8
From: flat out like a lizzard drinking Wisconsin
hissing in dash
i have same vacuum leak noise when unit is off or floor air is on no noise in defrost (2000 frc auto climate control) have not looked up
exact vacuum line but from other gms i have worked on 1 can assume
floor actuator diaghfram or line to it since no noise when defrost is
selected i have also seen round vacuum connector at control panel
not properly seated or broke/pulled out line on it if you tell me year
and witch hvac i will look up on service info for you
exact vacuum line but from other gms i have worked on 1 can assume
floor actuator diaghfram or line to it since no noise when defrost is
selected i have also seen round vacuum connector at control panel
not properly seated or broke/pulled out line on it if you tell me year
and witch hvac i will look up on service info for you
Melting Slicks
Joined: Sep 2006
Posts: 2,736
Likes: 7
From: Redding CA
Just an idea, but why not start with the electronic vacuum selinoid under the passanger side and work with each line to see if you can isolate it, as mentioned above. I can get you the infor on the colored lines so you can see what each goes to, but not until later tonight if you need that infor.
Advanced
Joined: Sep 2007
Posts: 61
Likes: 3
From: Duluth GA
I just replaced a couple vacuum lines on my '02 coupe, I'm getting the hiss only when (electronic) A/C is on and recirc is activated. The HVAC vacuum source line on my vehicle is a thin purple line which is accessible from the passenger side floorboard.
The purple line apparently goes into the HVAC system and is split to various control doors that route conditioned air through the cabin. I haven't gone past the purple vacuum line. My hissing sound seems to be coming from this area, but I haven't reopened the passenger side floorboard yet to explore.
You may start with the purple line in your search and go towards the HVAC, or follow the black vacuum source line (which goes to a vacuum reservoir canister behind the right front fender - this is where I had to replace the vacuum lines in my case).
Hoping this helps,
Anthony
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Advanced
Joined: Sep 2007
Posts: 61
Likes: 3
From: Duluth GA
Here's a link with good HVAC repair info regarding the vacuum lines:
http://forums.corvetteforum.com/c5-t...nge-vents.html
Anthony
http://forums.corvetteforum.com/c5-t...nge-vents.html
Anthony
Heel & Toe
Joined: Aug 2010
Posts: 20
Likes: 0
From: Calgary Alberta
Having a similar issue with my car as well. I've narrowed it down to the HVAC for sure since the hissing will change depending on if my HVAC system is on or off. The hissing I'm getting seems to happen when the HVAC is off though. When it's on it seems to disappear.
