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
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
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.
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
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
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
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.
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.
Well, then if this is the case, I'll have to open the plenum anyway, to
replace broken parts, right?
Thanks for helping!
I bought it via internet at http://www.manualsunlimited.com/catalog /
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
I found the schematic for the blend door electrical circuit. Thanks for the
I have removed the white rectangular motor. Yes, it's electrical, not
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.
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! -
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.
I can see the big flap. I just haven't been able to remove it for repairs,
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.
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.
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!
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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