Hey folks. Me again, the newbie to 3rd Gens and auto work in general.

So I’m having issues where air or heat will not blow from the vents, only the dash. I’m going to check under the passenger panel to see if the flap is opening and closing that causes it to switch between dash and vents.

But we are also having issues getting heat to blow. Stays cool. I do know the door that controls hot to cold is opening and closing. I’m wondering if these vacuum lines under the hood are my issue and potentially my issue with the dash to vents switch too.

The long hose in this picture runs along the side of the engine bay to the “top” looking part in the other picture. Doesn’t this have something to do with the HVAC or blower?

What does that other, shorter hose connect to? It’s completely disconnected and both are rotted out so need to replace but want to know where the other end of that shorter hose is supposed to run.

Thanks all!

 

The piece in your 2nd pic is a check valve.

Thimk for a minute about vacuum-controlled ANYTHING... what happens when you give the engine lots of throttle? The vacuum goes away, right? What are all those little doors and things going to do? Well, they're going to return to their "rest" positions until vacuum reappears, no? The cure for that is a reservoir that holds enough vacuum to cover the expected demands of accessories for long enough that everything stays put while accelerating. BUTT... there needs to be a check valve that only allows vacuum to "go" one way - FROM the intake manifold and TOWARD the reservoir and accessories - but doesn't let the reservoir's vacuum "drain" back to the manifold. That's what that check valve does.

The hose on the bottom of it goes to the engine, and is the "source" of vacuum. The check valve keeps vacuum from going the other way. The other 2 ports are essentially the same thing, just pointed different directions. The hose on top looks like the one going to the HVAC controls; the other goes toward the reservoir. The T fitting probably serves/served the cruise control. The reservoir is probably a ball about 4" dia in the fender behind the driver's side parking light.

Replacing the hoses will probably fix the whole thing, particularly if your car has a vacuum-operated heater control valve.

 

Thank you very much! But where does the other end of the short, cruise control, piece hook to?

 

:shrug: Cruise control. What else could it be?

 

Look for a round ball thing and or round canister under that washer fluid tank. Should be a vacuum connection to those, the ball is a storage and the canister is fuel tank emission deal.

 

The ball is actually right under the fuel vapor cannister which is shown right under the air intake duct

 

Oh, and if the ball is not there I think I have an extra one.
Just LMK in that case

 

Okay. So finally got under there today. I don’t see a ball thing under the windshield wiper reservoir. Here are some pics of the reservoir removed and the area around it.

 

FWIW here is one of the most helpful you tube videos I found to help explain it in a couple variations. They are not all the same, gotta love the 80's emission and vacuum actuated stuff. He has a few videos that show vacuum and removing the TPI where you can see some vacuum lines as well.

 

As I previously mentioned, it's under the fuel vapor canister which can be seen from under the car. It's mounted to the bottom side of the sheet metal that the canister is mounted on the top of..
The canister is shown on the left edge of the last and bottom pic in your series

 

Yep what Henry said, the video I posted was just to help check vacuum routing if needed. I had trouble with that before and it helped me a lot but not totally.

 

Hello, im having the same problem as my car is a 92 Camaro RS TBI V8 .. I can not get air to blow out vents, only coming from bottom vent on passenger side. I have same hose in your previous pics that’s also damaged.. did you ever find a fix?

 

You are looking for a black sphere, the shape of the one mounted on the hood of my 87 G20 in the picture. That is the vacuum storage tank. It provides reserve vacuum for the ac controls and cruise control when the engine vacuum is low. You need to replace all those rotted out vacuum hoses and plumb the system back correctly to the vacuum line going into the firewall, the check valve, the engine and the sphere. GM liked to play Where's Waldo with the places they mounted them on vehicles that had them. Some will have two spheres even, one for the cruise and a 2nd for the AC.

 

You should find it under the tray the Vacuum canister shown in the pics is on

 

I was not sure where it was in that model, but had a clear picture of what the typical GM vacuum reservoir looked like. Easy to find on the vans of that era, practically hits you in the face when you open the hood.

 

Well, that's where it is on my 92 RS with 5.0 TBI engine. If you don't have one there I believe I have a spare one around somewhere. And Yep, that's exactly what it looks like

 

I think I have 3 or 4 laying around in various sizes as well. There is one that is 4-5" diameter, a smaller ~3" diameter version as well as one that is more cylindrical that looks like a hot dog in a bun.