climate control "hissing" sound
 

not sure where to post this. my climate control has a hissing or air leak type sound that gets louder the farther you move it to the right. i also don't think i am getting enough air blowing from the lower vents when on the heat setting, or even on vent setting. the blower motor is working and it's noise level increases appropriately as you turn the level knob. is there a vacuum line behind the climate control? any other ideas? car is a 91.

Re: climate control "hissing" sound
 

So you have a vac leak somewhere.

Vent positions are changed by vac operated actuators operated by the programmer which is
controlled by the headunit

Vette system shown but F-Body vac lines would be similar


http://i171.photobucket.com/albums/u...cal/HVAC-1.jpg

Re: climate control "hissing" sound
 

so does someone know if those actuators are behind the climate control panel or exactly where they are located?

Re: climate control "hissing" sound
 

Stick your ear to the pass side of the HAVC. If the leak is there (and very often it is), you'll know. Here's what the vac lines look like:

https://www.thirdgen.org/forums/atta...duct010707.jpg

JamesC

Re: climate control "hissing" sound
 

Put your head under there and you can find them
Like shown in the sample Vette diagram, the actuators are mounted in various positions on the A/c ducting
under the dash where the vent doors are

Re: climate control "hissing" sound
 

Re: climate control "hissing" sound
 

The controls are on the HVAC control panel. Pull it away from the dash and you will see all the vacuum hoses.

The actuators (diaphragms) are only visible from the driver side if you stuff your head down by the foot petals. Two are on the end of the HVAC box, and one is behind it. There is another in upper right corner of the firewall that is the fresh air mix. Pictures of the actuators are in this post of my build thread,

https://www.thirdgen.org/forums/ltx-...ml#post5965742

Re: climate control "hissing" sound
 

Pull the control head unit. The hissing you hear is a leak where all the vac lines connect to the head unit. There is a plastic keeper that holds the vac lines to the adjustment part. The plastic keeper is in the center of the adjustment part. Replace this part and your hissing with be eliminated

Re: climate control "hissing" sound
 

Whats this plastic piece officially called?

Re: climate control "hissing" sound
 

I call it the "heater thingy."

Here's how you fix it for a couple bucks:

Re: climate control "hissing" sound
 

Did that repair on mine about two years ago. That was the end of my problem.

Re: climate control "hissing" sound
 

I did the repair after ordering the new selector. The repair stopped working so replaced the old one with the new one. Now, it's stopped working. So, going to try this repair on the new one. If that doesn't get it, not sure what to do. Sucks that I finally got the AC working but can't get it to come out the proper vents.

EDIT: took the new one and the old one and made one. this time, used the nut/bolt method above. used the old rubber piece because it looked to be in better condition than the "new" one, which was basically a refurbished one, i think. anyhoo, also, soaked the rubber part in brake fluid for 20 mins, give or take. tightened the bolt/nut fairly snug so that the mechanism worked fairly tight, but still slid. put it all back together and it works like a champ, no hissing and the air moves from defrost to vent to floor quickly.

fix worked. i think the first time i did it i was afraid of tightening the nut/bolt too tight which is why it didn't work. hopefully, this time it'll keep working. if not, i'll pull it, soak it in brake fluid and again and tighten it down some more.

Re: climate control "hissing" sound
 

Rather than soaking it in brake fluid, which deteriorates the rubber even though it softens it up in the short term, I'd suggest using dielectric grease on it when you put it together.

Re: climate control "hissing" sound
 

Re: climate control "hissing" sound
 

Two small push-on clips hold it in place.

JamesC
https://cimg5.ibsrv.net/gimg/www.thi...10de37a403.jpg
https://cimg4.ibsrv.net/gimg/www.thi...7a022478a3.jpg

Re: climate control "hissing" sound
 

those i have.. but on the other side there is another rubber fitting that doesn’t seem to have any kind of clip

Re: climate control "hissing" sound
 

I was editing when I noted your response. I don't recognize that piece offhand. It's not on the extra HVAC head that I have lying around, but perhaps it's missing a part.

JamesC

Re: climate control "hissing" sound
 

Re: climate control "hissing" sound
 

Seems like 99% of the problems are with the vent selector. Mine wasn't, mine was the smaller one on the left side that I would say goes to the valve for cars that have the heater hose bypass under the hood on the passenger side valve cover. After doing a simple fix I realized what it actually did. I've LS swapped my car and don't have the bypass anymore so I could do away with that selector. But for those that still have the bypass valve here's what I did to fix it.


https://cimg6.ibsrv.net/gimg/www.thi...cdcdfe6c5f.jpg
I put a felt type washer/seal and it still lets it breath but took away the hissing.
https://cimg8.ibsrv.net/gimg/www.thi...c51f3a7852.jpg
The notch moved to atmosphere when you slide the heater knob to hot. Releasing the vacuum on the heater hose valve.



Its supposed ti "leak" by disgen.

Hope this helps someone in the future.

Re: climate control "hissing" sound
 

I realize this is an old thread, but I'm hoping someone will help me out with either a part number or a parts source. My vacuum selector valve was leaking as discussed in above posts. when I tried to remove it to do the repair shown in the video the little star shaped spring fell out and into the abyss under my console. can't find the spring. willing to buy a whole new one if I could find one. Mine is a 5 port. No amount of "Googling has turned up the right one yet.Please help if you can. Thanks.

Re: climate control "hissing" sound
 

It's not in the abyss, it's the floor of your car. Take the console out and go after it.