lostnfoundC4

I've searched and read some really good threads on here regarding HVAC issues inside the cabin but can't find anything related to my problem.

My '86 has the early manual temp control and I recently noticed little or no heat and very little resistance on the blending control. The cable had come off the arm behind the unit.
It appears that the slide function/blend door works half way from right "hot" to center. Forcing the control further to the left makes the cable jump off the arm. This would explain little or no heat as the blend door was obviously in the middle. Something is definitely blocking the door from moving in it's full range. It looks like this door is controlled 100% mechanically. Am I missing something? Could there be a vacuum issue?

fredd1

I'm fairly sure the linkage is mechanical (not sure if it's a cable or a rod), although I haven't gotten in there to check yet. I'm having a similar problem on my '84 except I can't slide the control to the right. It moves about a half inch and meets resistance, so I'm guessing the door hinges are probably rusted/frozen shut. If I have time this weekend I'll try removing the HVAC control panel and see exactly what's back there.

lostnfoundC4

Thanks Fredd,

It is connected by cable directly to the box but something is impeding the movement to seal off the heat. I was thinking maybe there was a vacuum line that may also work with this.
There is not much room to work with in the foot well for access. I'm hoping I don't have to take the dash completely out to find out what's going on

vetteoz

Vac only controls vent positions ,not temp

At the controller or at the blend door itself ?
If at the controller, time to get under the dash , disconnect the cable and see if the blend door itself has full free movement.
If it does then you know problem lies with the cable operation

Cliff Harris

You can remove the resistors that control the fan speed from the evaporator housing and see the blend door through the opening.

The blend door is completely controlled by the HOT -- COLD lever. I have heard that the actuator rod bracket that is attached to the blend door can have broken spot welds and cause a problem.

lostnfoundC4

Thanks guys.


Cliff,
What is the most minimally invasive way to get to the resistor pack? Do the dash & crash pads have to be removed? Or is this something that may be accessible from below? Thanks

vetteoz

evaporator housing is in the engine bay
Undo the 3 x 8mm hex screws and lift the unit out
You can then see the blend door operation ( or not ) through the hole

lostnfoundC4

That was easy enough! I was able to move the door through it's full range from that opening. I'm going to try spraying some white lithium into the cable jacket to loosen it up a bit. I'm also missing the speed nut that holds the cable to the arm of the slide control. Hopefully I'll be able to feel around in there and find it. The initial problem was that the cable had jumped off but there is definitely too much resistance from the middle position to cold. Thanks for the picture

lostnfoundC4

Problem Solved!

The plastic cable clamp at the air box pulled away by about 3/4" so I made a bracket to make up the difference. It works great and will at least buy me a little time while I look for a bone yard replacement.
Thanks everybody for your help

bassackwards

I'd just leave that and button it up.