81_vette!

Is this hose related to my issue? (WH-Yellowish)


My issue: got fan at all four positions, got cool and hot air, but no air comes out of the top vents (only comes out of the passenger heater vents). A/C vent control (climate control module) has been replaced.

No air flow from any of the lower "ball" vents.

I have replacement hoses on the way.. and as I understand it my lower vents door is stuck in position? Is the door actuator in the dash where I need to be looking?










New owner of a 1977, just working my way through a few issues.

bruiser

The white hose goes to the heater core shutoff valve. You are probably
better off plugging that hose and get a manual valve from Home Depot
to put in line on the heater hose. For the vents not switching,
the problem is usually the vacuum switch on the control panel.
http://willcoxcorvette.com/product_i...ducts_id=12686

81_vette!

This is the information I am trying to figure out:

Posted by Ganey

The problem is that heater is the default position (no vac. or vac. leak)

*** If you have a heater, the small vac. tube to heater hose valve underhood may be damaged from heat & need replacing.***

Is this the hose pictured above?



The vacuum switch on the control panel is brand new and seated properly to the vacuum hoses.

81pilot

YES, mine popped off and the vents would not blow on top only bottom. It went to a three way vacuum line on the right side on my 81, the T had broke, I got another at Autozone and wham it was fixed.

81_vette!

Sorry to be such a dufuss.... but what popped off?

The actuator door in the dash?

Or the yellowish vacuum line under the hood? (and if so, what does the yellowish vacuum hose connect to?)

81pilot

well on mine it was a different line. But if you look at that diagram, you will see that line goes to and ties into the other vacuum line that pulls the vacuum that operates the actuator door. It looks as though that yellow line goes to your heater control valve, it is probably not allowing enough vacuum for your actuator door to change states. Try plugging the yellowish small vacuum line and see if air blows out of the upper vents. Mine was the black line going to the T on the left of your diagram, but follow them and you can see they are interdependent on one another to a certain extent. It can eve affect your headlight operation.

81_vette!

That did it! So easy.... I just put a dab of silicone on the end of the loose hose to block it off and shazaam... the upper vents (and all others for that matter) were blowing out air!

Thanks a million for the quick and easy fix!

81pilot

Now. That line looks like it goes to the heater control valve. That is a valve located inside the engine compartment and inline on one of the heater hoses going to the heater core from the water pump. What it does is shut off the flow of hot coolant to the cabin during the summer and open when you need it in the winter all controlled by the AC controls via that line. Some guys put a simple shutoff valve instead of the heater control valve like I did. So it is possible it has already been removed. Look up what a heater control valve looks like from a parts house and you will know what to look for. Congrats on the blower fix. The vacuum systems on these cars are so interrelated that a line from one thing being off will cause problems with something else.

Jimsal

I have the same problem on my 81, I also see in the drawing above that there is vacuum to a brake booster, I also am having some problem this season with my brake coming on when I apply the brakes. The car stops OK but not like it should could this be a vacuum problem as well?

iwannanSC

That yellowish vacuum line that runs to the Heater Control Valve - any idea where that can be purchased? Is it generic-size vacuum line or something specific?

C3 Vette Dude

The vents in my 79 only work on the floor as well. My yellow vaccum hose broke off in the fire wall. If I just put silicone over the hole what will if effect later or should I fiqure out how to attach a hose to the broken end and connect it ti the HCV?

paul8755

Hello
I got the exact problems that you have with your corvette.
Could you please take a picture of your corvette's engine to show exactly where the white cable is connected to please, mine broke and i don't know where it goes

My issue: got fan at all four positions, got cool and hot air, but no air comes out of the top vents (only comes out of the passenger heater vents). A/C vent control (climate control module) has been replaced.

wwhelch

So my problem is on my 72 I get hot air with the ac controls in the off position. So by reading this thread is fails to heat correct? I have to have a vacuum leak somewhere, maybe the white hose? Also have a problem where my wiper door opens a little after I shut the car off. It close tight when running. Vacuum problems on this car are crazy. So where should I start?

paul8755

Hi
you may text me at
(661) 400-9819
i just repaired my Corvette vents

pl2000n

This thread is incredibly helpful! First, yes, the heater control valve fails open which allows hot water to flow (which is the exact problem I have). My wipe door exhibits the exact problem you are having. My engines pulled at the moment, but I have a vacuum pump to experiment with and will hopefully expose the trouble part(s). I can't, however, see how a failed heater control valve circuit would directly affect the wiper door and not other components too (such as headlights). I'm thinking the wiper door relay is leaky, and lets vacuum allow the door to lift a bit.

NRAROX

My 68 would only go to middle registers / outlets or the floor (no defrost). I had to pull the heater core box to replace the actuator behind the box. Ugh! Long story. Test the actuators width a vacuum gauge if this doesn't fix it. As I recall, they should 'hold' 12 pounds or so. Mine in the rear would hold on one side but not the other. This actuators's resting state is Bi-level. Good luck.

wwhelch

Thanks for the responses. I found the problem, one the passenger side there is a solenoid that was not plugged in and vola that fixed the AC and the heat problem. I had to get to it from under the right passenger side by the louver. I also figured out that I have a hose leak from the wiper door actuator to the one located on the passenger inner fender well. Once I replace those hoses all should be fine.