Heating question

[Daytona#3895]

On my 87 V-10, while in the cold position, i can move from defrost to floor to vent and everything works properly blowing out cold air. If I move it to heat, it will only blow out the vents and nothing out the defrost or floor no matter where I put the selector. My question is, why would the selector work when blowing cold air but not hot? Thanks in advance for the advice. Snowed today and need the defroster.
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[bake74]

     I am not sure about this one, some one who has had this problem will chime in when they see it.

[Daytona#3895]

I hope so. Would rather wait for a response then have to disassemble everything to find out it was something simple. Just doesnt make sense. I didnt think the hot/cold blend door would affect the other when selecting floor-vent-defroster. Dont understand why it will  work when cold air is selected on defrost and then moving to hot and it diverts it to the vent only.

[Harmon]

I have somthing along those lines too...When I have the Air on OFF, I get alot of "Wind" coming from under the dash...Im interested to see what people say about your issue.

[1980c10]

I dont have any idea what is going on with this issue. I do think I would start by just looking under the dash at the cables where they hook up on the heater box while someone moves them and see if they have the full range of movement needed.

[VileZambonie]

First make sure the vacuum reservoir is connected and functioniing properly.

[Harmon]

Daytona did you make any progress?

[mattgood]

I ran into this problem once on an econoline van. I can't remember which was working a/c or heat, but it was a similar problem. If there are any vacuum lines check all of them for leaks. Some vehicles have vent doors that are vacuum operated so I would check that out. I believe we had to replace the resistor block which the lines hooked up to. It was a few years ago so I can't remember exactly, but I hope this helps. I would also just locate the vent doors and make sure they are not seized for some reason. Good luck.

[ehjorten]

So there is only one thing that links these two levers together and that is at the temperature door itself.  The temperature door is connected to the diverter door or whatever it is called via a short, flat link.  That link goes through a bell-crank and is attached to the diverter door that is operated via 2 vacuum pods.  It could be those 2 vacuum pods are not functioning properly (probably the one mounted inside the heater distributor box and not the one on the outside of the box.  The reason I say this is because that vacuum pod is connected via a short length of rubber hose and that hose dries out and get brittle over time.  The other thing maybe that the two doors are not connected anymore because the rivet broke or something.  I have had both happen to me!