I can't for the life of me figure out where the mechanical cable for the air selector (vet / floor/ defrost/ AC ) connects to the circulation system. The whole cable is missing so I have nothing to follow. The heat range cable is still there and works.

I have one diagram from Haynes that isn't too helpful and another from Ford which doesn't actually show where the hookup cable attaches on the air ducts. I've looked all over and can't find anything that looks like it's a cam for the cable other than something that looks like (and is attached to) a vacuum motor of some sort.

If anyone can point me to where it connects, I'd really appreciate it

 

There is only one cable used. That lever is just a switch.

 

On all F-series, the ventilation system is vacuum-operated except the cable Temp selector, EXCEPT '87-88 which is all cable-operated except the vacuum Max/Norm (recirc/fresh).

You should diagnose a broken vac line, a leaking vac motor (diaphragm), or a leaking selector at the control panel (needs vaseline).

 

Not to be ungrateful or anything, but it really looks like it goes to a second mechanical cable. The haynes had a diagram of an "early model" air selector and it had a 2 mechanical cables (one temp control, one air selector). The levers in back look like the ones in my truck

The only thing I can think of is if the switch in the truck is not correct for the year it is. The Ford dealer's CPD diagram show it as having 2 cables also, with different part numbers for each (18518=heater cable, 18552=air selector cable). Unless they have the year of my truck wrong... (they haven't steered me wrong yet, but they are a dealer)

I do appreciate the input. Any more thoughts? If it doesn't connect to a mechanical cable what does it connect to? There are two things that look like vac motors, but neither looks like it has a vacuum source attached to it or a place to hook one up to. I can verify this tommorow. One is completely vertical (circular ends point up and down) and the other is horizontal with a wire that goes to the switch body (a/c related?) The vertical one looks like it actuates the lever going inside the air system.

Of all the things i've fixed, this is the most frustrating so far (lots o conflicting information). And while I don't need heat in TX i'm moving to IA where it's freeeeeezing!

One other item, this truck is 1983 F250 XLT with A/C, though many of the a/c wires were cut/rerouted/altered by the previous owner (*******)

 

The control panel was made to work with cables or vacuum, and on F-series, it's vacuum. If you look more closely, you'll see the arm that moves with the selector also has a tiny arm going into the vacuum conrol box, where all the vacuum lines are attached.

 

The selector lever is the same part for all models, but has the cable for only trucks WITHOUT a/c. For a/c trucks it operates a vacuum switch like previously described.

 

Ok, there are 2 wires coming from the vertical vac motorish thing. One is blk-red, the other is blk-yellow. Both go to the switch body. I found the rheostat on the back of the switch, so i can see how it can send a signal without a mechanical cable.

I still can't see where a vacuum line should hook up to this thing (could it be electric?). I also tried moving the arm by hand and it wouldn't budge...is that normal or does it indicate a problem?

Here's a picture of the motor so you can see for yourself:

http://www.timekill.org/picts/airselect_actuator.jpg
http://www.timekill.org/picts/airselect_actuator2.jpg

 

Played around with it a bit. It appears those "wires" are hollow as are the places they plug into (i.e. very small vac lines). I was able to actuate the lever with my handpump through about 90 degrees of rotation (is that normal or should I expect more/less?) when connecting it to where the blk-yellow line was (top of actuator). Pumping out the lines showed they wern't holding a vacuum (engine off), so no kinks in the lines. Pumping out the actuator where the blk-red line connects didn't result in any arm movement. Any ideas on what this line does ? ( My guess is to equalize pressure when the switch is moved back to OFF or something, but then it doesn't really need an actual line to do that)

I also looked at those cut a/c lines and they look like vacuum lines too. If these are cut (and thus vacuum leak), will this affect other vacuum operated controls? (one of the cut lines was blk-white).

Still tracing where the vacuum source line is

Thanks for the help!

 

Starting at the intake manifold, there is a vacuum tee that several lines should connect to. One of them runs to the top of the firewall, slightly R (passenger side) of center to a small black plastic vacuum manifold screwed to the firewall. One of the lines coming off it runs R to a 3-way check valve. One of THOSE lines runs to the vacuum reservoir on the R wheelwell and the other goes thru the rubber grommet on top of the ventilation box against the firewall under the R hood hinge. THIS IS THE SUPPLY LINE FOR THE VENTILATION SYSTEM. A second line comes back out to the recirc/fresh vacuum motor right there.

The supply line should run to a clear flexible rubber connector (with about 4 other colored vacuum lines) that's connected to the vacuum control box on the back of the A/C control. The other lines run to: the fresh/recirc motor (as mentioned), the panel/defrost/mix motor; & the floor/panel motor.

 

It appears the vac was disconnected between the engine and the black doodad. The black thing has 3 ports, one goes to the tee, one should go to the engine, and the last is also missing. I'll put in the appropriate hose and cap the empty one and see if that fixes it. Haven't traced the vac feed line in the cab..haven't found where it is in the cab yet (I can see where it goes in from under the hood)

Thanks for the description of the vac lines. I never would have put all that together on my own.