Shark Racer

When I have the car on heater, I can feel the heat pour out of the floor vents, but when it's on defrost, nothing comes out of the top vents.

Don't ask how I fixed the heater, I just unplugged and replugged visible vac hoses... how do I go about replacing all the hoses in the heater system? Do I need to pull the dash?

BTW, BobChad- that diagram is awesome! Thanks mucho.

Thanks in advance!

-Steve

cchristo

There are probably several things that it could be but I'll talk about mine. The problem was that the cable needed adjusting. There is a wire cable connected to the position control on the console. On mine anyway ('80) there is a plastic adjusting nut that controls the cable travel. Too much travel and air won't go through the floor vents, not enough and it won't go through the defroster vent. You can get to it by removing the right side transmission console panel. Be careful because the heater/AC control panel mounting system is pretty fragile. If you have good vacuum, this is a possible cause.
Hope it helps.

Ganey

Sounds like a vac. leak. You should not need to replace all the hoses in the heater system or pull the dash.

FAST FIX by GANEY
On at least later C3 the problem is that heater is the default position (no vac. or vac. leak) due to being designed in the north. Vent should be default. Very safe bet the problem is 1 OR 2:
1) The vac. line from engine is damaged from heat - a small plastic tube that goes in below the hood theft switch into wiper valley. Replacing most of engine side w/ hose will fix. OR
2) The vac. switch itself is not switching due to vac. leak as the usually plastic rivet is not holding the 2 main switch parts together well. Besides replacing, it is also possible to tighten this &/or lube w/ white lithium grease or vasoline to fix.
3) If you have a heater, the hose to heater hose valve underhood probably also needs replacing. Block w/o heater.

PS The design problem comment is not intended to be offensive to any of our northern friends.

:cool:


[Modified by Ganey, 12:24 PM 12/21/2002]

MoMo

On the C3, the early ones at least, the heater/vent/defrost controls are via steel cables. Mine were all messed up when I bought my 68, but just needed reattaching and lubing. You'll at least have to take off the passenger side dash panel, and possibly the center gauge console to reach everything.
The later C3's might use vacuum-actuated flapper doors, I'm not sure. You'll still have to get back there to check everything out.

virtue4u

I had this problem for over a year and could not figure it out. I tried two new GM actuator switches, traced the vacuum lines, measured the vacuum, listened for hisses. Nothing seemed to work. The fix was easy. I took one of the new actuator switches, opened it up and applied a thin film of vaseline to the interior surfaces. Voila! The defroster worked immediately. Moral of the story: even the new actuator switches need a little sealing lubricant to work correctly. Hopefully, this is your problem. I probably could have simply applied the vaseline to the old original switch to solve the problem.

cchristo

I've saw a lot of posts in the last few days advocating the use of vaseline on rubber things like vacuum seals and the like. Someone correct me if I'm wrong, but I'm a bit wary about using it. Does'nt vaseline destroy rubber? I know that there are certain rubber sealing devices (some of you may know what I'm talking about! :blueangel: :thumbs: :reddevil ) that specifically warn against the use of vaseline as a lubricant. If it's bad for those, isn't it bad for the car?