Heat in car. Defrost/vent/under dash....
 

Gents....

Fan is working ok. Speeds are ok
The other control for the defrost/vent/under dash is not responding at all.
When I engage high speed fan, I have heat blowing
out at the 3 outputs.
I can't seem to direct the heat at one place only....

I've briefly discussed this with Ron and he mentioned something about the numerous small tubes under the control console.
I've dismantled the side panels and can see the obvious 1/8 plastic/rubber tubes going up further in inside the dash.

Can anyone give me some advice on what should I check next ?
Crap ! Hopefully there's no need to take the dash out again !!!!!

Any diagrams on this ?
When I installed the new dash in last summer, I remember lining up the vents properly and sealing the gaps at certain areas. I don't recall pluging in several 1/8 tubes. Maybe they were untouched and stayed connected during the overall....

Input anyone ?

Phil

It sounds like your system is in the fail safe mode in which air is directed to all outlets in the event of a vacuum failure so I would check to make sure that the vacuum connection is connected under the hood. Another place that you may be having trouble is at the vacuum "switch" on the heat/AC controls. I'm not familiar with the controls in a 1980 but I suspect they are very similar to earlier years. That switch can "leak" and cause problems with the system as well.

Here is a link to the C3registry that has a lot of documents specific to the 1980 Vette. I looked at the one for heat and air controls but it talks about the electrical side not the vacuum side.

http://www.c3registry.org/index.php?...loads&uid=6742

Regards,

Jay

vacum connection ?
 

Thanks for your assistance Jay !

That site is pretty sharp but unfortunately not telling me exactly what I'm looking for.

You mentionned about a vacum connection under the hood. Where would that be ?
Do we see it in a diagram somewhere ?

Thanks again.

Phil

look at this not sure if your is the same
http://www.lbfun.com/warehouse/tech_...c_controls.jpg
what year is the vette?

Phil,

The diagram that cargo247 posted looks like it might be for a late 70's or early 80's Vette so it should be pretty close to your situation. The hose labeled source that points down is the hose I would trace and make sure that it is connected to a manifold vacuum source.

Jay

This is exactly what I was looking for !!!!
 

My vette is 1980.

The diagram is what I was looking for. I hope its the same for my car !
Will get it printed and dive under the dash to investigate !!!!!

Anyone else that could confirm if the diagram applies to the 1980 model would be great !

Thanks all !

Phil

I wrote this up awhile back for this.

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. Check:
1) The vac. line from engine is damaged from heat - a small plastic tube that goes in below the hood alarm 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/ a thin layer of white lithium grease or vasoline to fix.
3) If you have a heater, the small vac. tube 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:

One thing you can do to eliminate all heat in the heater core during the summer is install cutoffs in the heater hose lines. A lot of the members have done this, as the cutoff switch on the C3 doesn't fully close most of the time. I know this doesn't address your vaccuum issue but it does solve an age old problem with heat in the cockpit.
Bernie

good idea but....
 

Hey Bernie.
Thanks for your help but I kinda need the heat at the windshield.
Unfortunately I reside in an area where there is lots of white crap on the ground and Spring and Fall seasons are cool.:(
Sometimes cool enough where I need to defog my winshield ! So I need a hot air concentration at the windshield vent

thanks