Is '98 van climate control dial mechanical or electronic?

My '98 Club Wagon has heating, venting, and air conditioning. When running the heater or vents, the air is maximum-hot all the time. Until recently,
we could regulate the temperature by turning a dial in the center of the dash board.
I have a CDROM service manual for this vehicle, and I can readily see the generalized descriptions of how flaps are arranged, depending on whether one is using the heater, vents, a/c, and whether the temperature dial is set to cold, medium, or high. The problems in troubleshooting are many, though. First of all, it is very difficult to access either the dial or the heat exchanger. So unlike an old truck with lots of room under the hood, this vehicle is nearly impossible to casually inspect.
I first assumed the temp dial was purely mechanical, with a cable directing the extent to which a "hot air" flap would be moved in the heat exchange plenum. However, the dial sweeps perhaps 300 degrees, which would be hard to accomplish with an old-fashioned mechanical linkage. So can anyone corroborate that my temperature dial is a potentiometer?
If I have a potentiometer as a hand-controlled dial, then the heater flap must have a rather fancy actuator. Any descriptions would be most appreciated.
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I found something: The temperature selection is accomplished with a potentiometer connected to the electric blend door actuator that controls positioning of the temperature blend door. Movement of the control knob (18519) from COOL (Blue) to WARM (Red) causes a corresponding movement on the air temperature control door and determines the temperature that the system will maintain.

one
to
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The manual should point out that the blend door is controlled motor, not cable or vacuum. What manual is this Ford factory or aftermarket?
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Aftermarket...and not terribly accurate. The manual says the blend door is controlled by a vacuum motor - 18A318. Indeed, I have found such a motor, identically specified, for the "air inlet door" (fresh vs. recirculated). The latter is to the far right of the van, inside the cab, above the location of a passenger's feet. The blend door motor is nowhere to be seen, though, and this is exactly what I need to accomplish. The manual says it's high in the dashboard, above the radio. I don't think so; even though I can't remove the radio (arg!) I can still see that nothing stands above it, matching this motor's description.
I think the motor might be inside a plenum. I see a vacuum line going in there. Could this be the case?
What a tough vehicle to work on!
"pick one" <try again!> wrote in message

cable
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Thanks for the timely advice! I should have waited...I have the plenum partially disassembled. Oh well, I can put it back together. So I see a rather flat, white box, inside the van, under the dashboard, at the far right, on the right side of the plenum. I can see it because, as you recommended, I have removed much of the passenger-side lower trim.
I can't work on the car, itself, anymore tonight. But tomorrow I'd like to test as much as possible, without any more disassembly. Do you still maintain that the blender door motor is electrically-actuated, instead of vacuum-actuated? So far, you're batting 1000, and my manual is batting about 100. I was hoping it would be vacuum-actuated, so that I could easily evaluate the motor, and its control lines.
Is this some sort of common fault, with a "typical" cause?
"pick one" <try again!> wrote in message

rectangular in

place
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of
changes, DC

The manual is ambiguous on the nature of the blender door actuator. I found a vacuum circuit diagram, showing several hvac actuators, other than the blender door actuator, as vacuum-driven. The electrical schematic eludes me for this part of the car. I will assume you are correct in calling this actuator DC-electrical in nature. Besides, the distinctive appearance of the the white, rectangular actuator implies it is not vacuum-driven, as a diaphragm is not apparent.

motor
The computer view of the CDROM has got Ford's logo all over it. Maybe it is genuine...or not-so-genuine, Ford. Hmmm...I wonder. No logo on the CDROM.

available
complete,
Well, then if this is the case, I'll have to open the plenum anyway, to replace broken parts, right? Thanks for helping!
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"pick one" <try again!> wrote in message

instead
found
eludes me

rectangular
apparent.
door
it is

CDROM.
I bought it via internet at http://www.manualsunlimited.com/catalog /

assembly. Well, they might be an assembly, but the shaft would extend through the wall of the plenum, and the blender door operates within the plenum, correct? Then I would have to open the plenum to replace such an assembly. Hopefully, the plenum separates where the shaft penetrates it at right angle; that way the assembly lifts out once the plenum "cap" is removed...which itself is a difficult accomplishment. I haven't done this before. I am merely visualizing what I expect is present, based on what I see in the car, and based on the description of operation of the hvac system in my CDROM. The CDROM has illustrations of flapper door positions, for the various modes of operation of the hvac system.
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*G444`%%%% '_V0`` ` end
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I found the schematic for the blend door electrical circuit. Thanks for the encouragement.

assembly. I have removed the white rectangular motor. Yes, it's electrical, not vacuum. The motor assembly came out easily, after removing the wire connector and four screws. Well, like I said, it came out easily...too easily. There is a shaft on the motor, but no flap. A screw hole in the end of the shaft is conspicuously empty. The flap has fallen off, and therefore lies inside the plenum. The screw has to be in there somewhere. So I will take the plenum apart, with great difficulty, to recover these parts, and then reassemble. As the shaft is nylon, I am not sure if Lock-tite will bond the screw or not. I don't want this problem to repeat.
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Jerry opined

If nylon, will have to be mechanically (read "creatively) bonded... i dont know of any adhesive i would trust. The screw COULD have simply not been tightened properly, though. If nothing broken maybe a longer screw, same thread with a locking nut
--
- Yes, I'm a crusty old geezer curmudgeon.. deal with it! -

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is
the
plenum
There is no screw involved. The big flap inside the plenum, which I have opened up, is movable with my fingers, by grabbing the end of the flap. I haven't been able to extricate the flap or its plenum frame, yet. It is very difficult to work on.
The position-driving motor works fine. I have caused it to rotate from one extreme position to the other, with the car "on" and while I turn the temperature knob on the instrument panel.
I can't get the motor shaft to mechanically attach to the flap, no matter how hard I try. There is no conspicuous breakage. I will try to form a better inspection. The heat exchanger, conspicuously visible now that the plenum cover has been removed, is blocking my ability to extricate the flap and its plenum frame. I am looking to see if it is "heat" or "a/c"; hopefully the former.
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No screw, but yes the shaft is broken common. Because the flap is inside the plenum chamber you cant see it, you have to remove the cover assembly.

Oh quit your crying it's not hard. My god!

The shaft is hollow that is why it breaks, glue it all you want it will not matter.
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the
I can see the big flap. I just haven't been able to remove it for repairs, yet.

not
I will have to remove the heater core, to get the plenum sufficiently removed to effect a repair. Though no breakage is conspicuous, you are undoubtedly right. There is an absence of mechanical linkage between the motor's remaining nylon shaft, and the flap.
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The cover is removable WITH OUT REMOVING THE PLENUM is an in vehicle repair. How many times and ways do I need to say this? The "absence" of "mechanical linkage" is the missing portion of the shaft which is straight, I.E. no bends. It comes straight out the box and into the "D" shaped hole in the motor. It's on the floor of your van in many pieces. How do I know this? I do this for a living, been there done that. Go to your local Ford dealer, purchase the blend door cover assembly, remove the old one install the new one done in about a 1/2 hour, no more.
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the
repair.
"mechanical
bends.
It's on

blend
a 1/2

I got the heater core out, after draining radiator and busting knuckles on "quick connect" heater hose joints. I borrowed tool from Autozone for such joints to no avail. OK, I didn't remove the plenum, but I removed the cover. After removing heater core, I extricated housing of blender door, and blender door. I have removed blender door from its housing, by drilling plastic axle. Will restore with nylon bushing. The cause of all this trouble is, as you said, a broken receiver sheath for the motor shaft. The shaft, "D" shaped in cross-section, is just fine. The "D" shaped sheath I reconstructed using epoxy in several layers, with fiberglass strands. I have inserted motor shaft, to test for proper fit. Should be tougher than new. I think this member is underdesigned, based on the frequency of breakage that your comments imply. There is plenty of clearance on outside of receiving sheath. You have a point, in recommending purchase of replacement from Ford, but I can't wait until Monday. Your help has been tremendous. Any further comments very welcome, indeed. If I have to to this again, I suppose I will do it more rapidly, but it will still take me many hours. So now my car will have a proper heating and ventilating system, hopefully. We like to use the vents, so that the traffic noise can be kept out!
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This is reassmbled now. I tested the blender door, installed, without plenum cover. It worked great. Thanks for your help. The only thing left for me to do is to reassemble the heat hoses, onto the heater core, and to change the radiator juice.
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