Interior Heat ... Defrost

[drcorvette]

Took the Vette out for a spin today and discovered I had no interior heat. The blower works fine but only blows cold air. Any suggestions????

Car runs fine with no overheating or coolant leakage.
Rad and overflow bottle levels normal.
Heater Core replaced about six months ago.

How does the heater door assembly work in an '85. Does the heater defrost leever manually open and close a cold and hot air door under the dash??? Could this be my problem???

Gary ............

 

[berky2500]

Have you used the heat since the heater core replacement? All of the door controls for heat, A/C, vent, def, etc are vacuum controlled. When you move the controls to each position you should be able to hear a small exchange of air as the door is repositioned.

There was a post here a couple of days ago from someone who had a hungry mouse dine on the vacuum tubes behind the dash. That would probably be a good place to look. I know I pulled a huge mouse nest out of that section of my dash the first time I opened it up after buying my car. Mine was sitting for a while before I bought it.

I'm not sure where the vacuum connects in the engine compartment...Pulling the center bezel and radio gives decent access to the heater controls and wiring.

Good Luck.

 

[drcorvette]

Berky

I am almost positive that the heater and defrost worked three days ago .... think I turned the defrost off because it was too warm.

Is there not an arm of some sort that opens and closes the heat door then the slide is moved back and forth????

When moving the slide from off to the first position I believe I can hear a door sound of some sort but sliding it all the way over to defrost I can hear nothing. There is no heat to the floor or from the defrost ... just cold air.

Gary

 

[berky2500]

There is a cable that opens the heat door but it is connected to the cold/hot lever on the bottom to open the draft door? over the heater core.

I had the entire dash out of my car and when I disconnected the HVAC controls, the only things connected to the top switch were a vacuum manifold and an electrical connector. I just looked at a picture of the HVAC controls again and I don't see anything mechanical (though I don't have a picture of everything connected for some reason).

I took my controls completely apart and cleaned them because they were very stiff and the blower motor didn't run at all. When I put it back together the blower motor works in every position, and all of the other controls seem to work correctly. Unfortunately though, that is the extent of my troubleshooting with these controls. Cleaning took care of 90% of my problem, but it sounds like you had something fail, though I'm not sure what.

I'm also not sure that there weren't different controls based on A/C or no A/C (though I doubt it).

After re-reading your post though, it looks like the air is getting directed to the correct place it just isn't heated. So maybe I'm leading you in the wrong direction. The vacuum controls where the air comes out, but not the temperature. The lower switch has a cable that is connected to the heater core. There is an adjustment buckle in the middle of the cable to get the door fully open when in HOT and fully closed when in COLD.

 

[drcorvette]

Update

Well last night I got in the Vette and pushed the heat leevers back and forth a couple times to see if I could hear any vacuum noises. Could hear something but not sure whether it was a vacuum sound or a door opening.

This morning I started the car and ... there was heat. So I am thinking something might have just been stuck. Not going to leave it at that though, rather will investigate further.

Gary

 

[JonM]

These may help you out with your investigation...

 

[berky2500]

Hi JonM,
Are those diagrams out of the shop manual or another manual? I need to get one, but I'm not sure which one has all of the diagrams and schematics, the shop manual or the repair manual?

 

[JonM]

Shawn...they are out of the Helms supplement (electrical) It comes with their manual. (mine is for an 84)

 

[drcorvette]

GREAT!!!!

Thanks Jon ... those diagrams will be real helpful!!!

Gary