Heater control cables with A/C

[northerngmc]

I am only getting air to come out of the A/C balls on the side of the dash and the centre duct above the radio.

I have tried moving the controls into all possible positions and still only have the A/C vents getting air to them. Nothing at all coming out of the heater/floor vent or the dash/defrost vents.

I have looked up under the dash and the cables are free and moving.

The lower control for heat seems to work fine and I can control the temperature of the air.

The owner's manual states that with the top lever when you move it to the outside air position ( almost all the way to the left) the vacuum control should open the door in the kick panel on the passenger side and when you move the lever all the way to the left, marked inside, the outside air door should close. When I start with the lever all the way to the right, the outside air door is closed. When I move it to the left about in the middle it seems to get a lot easy to push and in the outside position the outside door is not open. If I push the lever all the way to the left, to the inside position, the outside air vent in the passenger side kick panel will open. This is with the truck running. I tried adjusting the cable by pushing it all the way to the right, which retracts the cable, and adjusting the cable end to the full retracted position. Still no better.

Any ideas?

I do have a 69 service manual but it does not really cover how to adjust the cables.

Oh yeah, this is on my 68 C20, 396, turbo 400 with factory A/C. The belt is off the A/C and I am waiting for parts to get the A/C functioning again.

[northerngmc]

ttt for the morning crowd....


Anyone had a similiar problem or understand how to adjust the top lever cable?

[northerngmc]

PLEASE somebody must have set up an A/C lever setup and know how the controls are supposed to be adjusted......

[wwotr]

Originally Posted by northerngmc

PLEASE somebody must have set up an A/C lever setup and know how the controls are supposed to be adjusted......

Well I'm kinda in the same boat, but my Mechanic is doing all the adjusting/Installation of the Cables, Ductiing, New Heater Lever Box.

[Lee H]

OK, I'll give this a shot. Will assume all the cables and hoses are in there proper locations. It sounds like the middle lever is not working the deflector to push the air either to the balls and center vent or to the heater/defroster vents. You'll need to get on your back and look up under the rear of the heater/AC housing in the cab and move the lever and see if it's moving the deflector. May have to remove the cable and operate by hand to see if the lever is moving it the full range.

[71meangreenc10]

Sounds like the deflector is broken, you can take it apart and push the flap to get air out of the defrosters, I have done it two years in a row to get the heater working right, havent figured out wheather to get my new ac kit or just replace the deflector box.

Smitty

[48richard]

I second that - there's a good chance the flap in the AC diverter box (middle of the three boxes under the dash) is broken. The cable will work the lever on the shaft but the flap doesn't move. I was able to repair mine with epoxy earlier this year, but it probably won't last. New boxes are about $100!

Richard

[northerngmc]

Thank you to the Saturday Truck GODS!

I will try and find some time today or tomorrow to get back to this.....

[KEL]

Hey
I was away for a few days.
I have a 72 with a/c pretty much original.
My knowledge is somewhat limited, but I can provide you with pics, and
how my setup works. If you need more after the info you have gotten, just let me know.

[sameyrasmea72]

Here is a pic. The flap is plastic and in is usually cracked over the years. When you move the lever only the part that is attached to the spine or hinge move and the flap stays in the same place.

[northerngmc]

Thank you very much to the truck gurus.....

Yes my flapper is cracked/broken at the base and while the shaft and cable move fine the flap does not.

I may try and repair with epoxy just to get the truck back driving and order the part later.


I am still confused on what activates the vacuum to open and close the kick panel passenger side vent? The top cable moves a flap in the left side box, but I do not see what activates the vacuum.

[wwotr]

Originally Posted by northerngmc

Thank you very much to the truck gurus.....

Yes my flapper is cracked/broken at the base and while the shaft and cable move fine the flap does not.

I may try and repair with epoxy just to get the truck back driving and order the part later.


I am still confused on what activates the vacuum to open and close the kick panel passenger side vent? The top cable moves a flap in the left side box, but I do not see what activates the vacuum.

Gonna go out on a limb here (because my Mechanic is doing the work for me).
I "thought" he mentioned that something about the Center Lever also controls the (or works) in cunjunction with the Top lever.
"Brother Chevy Parts" does sell a "Lever replacement Kit", and their levers are made of Steel as opposed to OEM Pot Metal, if memory serves me right.

[71meangreenc10]

Northern,
There is a vaccum switch in the control unit that when its set to the right position the door gets vaccum to open/close.

You should check all your lines and see if they are still functional, mine still works and I here the door shut when the truck shuts off.

Smitty

[northerngmc]

Originally Posted by 71meangreenc10

Northern,
There is a vaccum switch in the control unit that when its set to the right position the door gets vaccum to open/close.

You should check all your lines and see if they are still functional, mine still works and I here the door shut when the truck shuts off.

Smitty

The vacuum door opens and closes, just not accourding to when and how the owners manual states.

The owner's manual states that with the top lever when you move it to the outside air position ( almost all the way to the left) the vacuum control should open the door in the kick panel on the passenger side and when you move the lever all the way to the left, marked inside, the outside air door should close. When I start with the lever all the way to the right, the outside air door is closed. When I move it to the left about in the middle it seems to get a lot easy to push and in the outside position the outside door is not open. If I push the lever all the way to the left, to the inside position, the outside air vent in the passenger side kick panel will open. This is with the truck running.

Maybe with the diverter flap broken it is causing problems......???

[Murphy IRE]

I had all kinds of problems with mine. The diverter valve and the flapper valve were both shot. I "Gerry" rigged both. My vacuum control head was shot, so I went with electric solenoid switches on the heat and the passenger cowl vent. With winter coming and Hunting season here, I just jset mine to blow out the defrost. Black Duct tape works great! Oner other these days when I do a total restoration, I will get all the parts new and get it to work according to the labels on the assembly.
LOL

[northerngmc]

I was able to epoxy the diverter flap this weekend and get it working. I used a triangle piece of metal and epoxied it on to the flap and the rubber edge. Works for now and in the spring I will be getting the factory air servicable again and will replace the box.

So I have defrost and heat again!

The vacuum switch still does not seem to work properly. The door will open but I need to have the top lever in the far left side to activate the door. Owner's manual says the door should open when the top lever is just left of centre and then close again when all the way left for full A/C.