Heater control noise/hissing. Help

[bgall2]

My 78 has a hissing/vacuum noise coming from the heater control. I keep the temp control knob all the way cold/left and have to secure it to the fan control swithch to keep the hissing noise (not very loud) down. If I move the control knob to the right or even unfasten it the hissing starts. Sounds like vacuum leak or something. Any ideas about what it could be before I take it apart? Thanks.​

 

[Vettehead Mikey]

Sounds like vacuum leak or something. Any ideas about what it could be before I take it apart? Thanks.

You nailed it. It's a vacuum leak. Almost all the HVAC controls are vacuum operated. Not much choice but to open up the console to see what's leaking.

 

[6880 Mike]

...a vacuum leak....Not much choice but to open up the console to see what's leaking.

Yep.

 

[bgall2]

Thanks....I will open up the console and check it out.

 

[82ColEd]

Probably the same as it did in mine:

There is fastener (white plastic) that holds the knob with it's round bottom that distributes the vacuum from one line to the other, together. Mine had it's tabs broken off and was just laying in there, rotating with the switch itself, not holding it together as it should. After openeing up the console (on the passenger side) and taking it out the switch, disconnecting the soft gelly line attachment, i simply glued the white thing back into it's place (carefully as to not glue it to the moving parts!), and i dont have a hiss anymore.

Let me know if you have issue, that i can help you with but you should be ok.


-Stefan

 

[bgall2]

Thanks man, I will take a look when I get inside. Iis it just the 4 screws around the transmission shifter that removes the cover?

 

[Yoda]

Thanks man, I will take a look when I get inside. Iis it just the 4 screws around the transmission shifter that removes the cover?

I think what -Stefan is refering too ... is the side panel of the console There are 2 screws that hold the carpet/board onto the tunnel. I find it easier to remove the passengers seat, then the side cover If you don't already have a 1978 Assembly Manual, I strongly suggest you find one (eBay), when working on our old steeds, it is invaluable :dance ..

If you don't know where the screws are,... one is just below the dash, about 6" or so from the firewall midway in the panel, the other one is about 8" or so from the back of the console about half way down the panel. If you rub your hand back and forth on the carpet (side panel) you will find them. The screws are phillips head..

Take your time and remind yourself, you're bonding

Bud

 

[Bob Chadwick]

Take your time and remind yourself, you're bonding

Make sure you have plenty of beer because that's what men have when they bond and keep the kids away because you'll be using a lot of that language that men use when they bond.

 

[82ColEd]

I think what -Stefan is refering too ... is the side panel of the console There are 2 screws that hold the carpet/board onto the tunnel. I find it easier to remove the passengers seat, then the side cover If you don't already have a 1978 Assembly Manual, I strongly suggest you find one (eBay), when working on our old steeds, it is invaluable :dance ..

If you don't know where the screws are,... one is just below the dash, about 6" or so from the firewall midway in the panel, the other one is about 8" or so from the back of the console about half way down the panel. If you rub your hand back and forth on the carpet (side panel) you will find them. The screws are phillips head..

Take your time and remind yourself, you're bonding

Bud

Excellent. My thoughts are permiating Yoda's thoughts.. The Force is with You Sensei.

(Translated: Yes, Bud is 100% right, thats what i meant, sorry if i wasnt clear). I actually didnt take out the seat but carefully bend the cardboard back a little and i was able to get in there. Carefull, as you dont want that cardboard to break! Keep in mind, i am 5'10" and skinny.
If you cant get there, take out the seat for room..

Here is a pic of the AC Control Vacuum Valve (from Ecklers):

The tab i am referring to is in the middle of the round, showing the 2 tabs holding it into place. Here it's black, mine is white. If you'd rather replace it whole, they are about $12..

Good luck bending in there..