HVAC Doors help

 Was going to a dr's appointment this morning and couldent get the defrosters to work. I kept playing with it and all I could get was hot air through the dash panel. I have the glove box out and the radio out and can see the vacume pots moving. I pulled the bottom heater pelenum and that door is moving open and closed. Where is the other door that deverts it from the dash to the defrosters?

http://www.garysgaragemahal.com/hvac-systems.html

See if this link works. Click on integral AC.

If some one knows, is the door with the part number 18A361 the diverter door that sends the air up to the defroster?
Thanks Dave, I saw those when I was looking the system up. Un fortunatly there is no function description to go with part numbers and diagrams.

I think this picture makes it the easiest to visualize the flow:


[Ignoring the Mix position]
18A361 (mode) impacts flow between dash (vent) and defrost/floor
If 18A361 is closed off to the vents, then 18A478 directs flow between defrost/floor.


Sounds like you've ran into the problematic plastic hinge failure on the mode door.

A number of us here have done this repair within the past year or two. Some out of truck and some in

Karl on FTE did an excellent guide on this

From his opening paragraph:

kr98664 on FTE wrote

If your '80-86 Ford truck has factory air, you can expect the following failure to happen at some unspecified time. Your windshield will fog over on the inside, and when you select "Defrost" and turn up the fan, practically all the air blows out the registers on the face of the dash, instead of from the defrost nozzles.

Edit: corrected the name of the door to 'mode' as opposed to 'blend' which is the cable actuated temp door

I am stretching it here, but I believe there is a servo motor nearer the steering wheel which has two vacuum hoses going to it. My son had a stereo head unit installed and then began to have issues. I removed the radio and saw the servo to the left. His issue was a vacuum leak and was corrected when I reattached a hose which had been knocked off.

Dave, I have the radio and the glove box out and can see the vacume motors working. I was looking at the fact that the door that cant be seen was the one that failed, the 18A361 door.

As Scott so kindly pointed out, the only door you cant see move.

If I were you, Steve, I would listen to Scott!

I don't know - I am crossing my fingers that I am wrong.  Would be much better if it wasn't that mode door failure.

Scott, in this case you are 100% correct. After reading through what that guy had to do to change that henge, it appears that is my next venture

Thanks guys.

Just as a heads up, I found that door NOS with new foam and all for $65.00. As I dont have a shop to work in, it will make it a little quicker.

Sounds like the dreaded plastic hinge.    unfortunately the dash is going to have to come out unless anybody knows a way to get the ploon out without removing the dash.   Get some small cabinet hinges from the hardware store and use them, its a very easy fix, but getting to it is the problem.  I would avoid the nos door and do the mod regardless.  It is a very weak spot in all Fords of that vintage, the plastic gets brittle and there is no guarantee the nos one will hold up

Sorry to hear that Steve. Did you already purchase the new door?

Ok, first, the blend door is the one the cable works, it adjusts the temperature. The door that fails is the mode door, it selects face or floor. After it is in "floor" position another door the one with the two hose actuator controls partial or full defrost mode. I personally would try to find a newer inside duct assembly if I were going into it Ford made an improved design on the later trucks. I don't know whether it started in 1987 or later, but the 1990 parts truck had the newer design.

Thanks Bill - I was thinking 'blend' since it contains a partial position but mode makes more sense. Updated and noted this above.

What's the improved part in the later years? Did they fix this hinge and find a way to keep the foam on the doors?

The later door has a shaft that it swings on. This is a 1995 case, the small opening goes to demister duct for the side windows but could easily be covered. I don't have a picture on the 1990 case.

My plan at this point is to get into the dash as far as I need to to set the door by hand so I have heat on the floor and the defroster. . Because it has been raining/snowing and I have to work outside, I went a head and ordered the door and will fix it up before I put it in with different henges so I wont have to do this again, I hope. I have it torn apart most of the way any way just to try to figure it out, so I will leave it together enough to drive it untill the weather drys out some.

With the bottom plenum off can you stick a dowel rod (or similar) up through that door and see if you can poke the broken door over to close off the vent plenum? Likely will have to leave the rod in there wedged but might be enough to get you by for a bit.

Steve, the link above that Scott posted is what I used to determine that my blend door was bad. Also used it as a guide in disassembly. Great link for fixing the blend door and that gentleman did a great service to the concerning Bullnose owner.  Now, in the link he replaced his from underneath with the dash still on. All I can say is that would have been tight. I looked at it and thought....No way! With just a few screws to remove the dash and a couple bolts to bring the dash support out a bit on the passenger side, one can easily remove the the duct work and have easy access to the blend door. I rebuilt my door as he did with an aluminum hinge. It will never fail again. Good luck on this project, buddy!  

Agreed John and prying on it in colder weather would give me pause.

Adding this here just in case it helps - this is the description of the hinge I bought that worked well (as would many). I am thinking that just pulling the pin and rotating one side got it really, really close to the right offset.

Aluminum 5052 Continuous Hinge without Holes, Unfinished, 0.06" Leaf Thickness, 3" Open Width, 1/8" Pin Diameter, 1/2" Knuckle Length, 1' Long (Pack of 1)

There is still a listing on Amazon for it but the price is about $70 more than it used to be.

Scott, John,  Bill and George

Because of the rain, mostly melted snow and the mud. I am only gonna do what I have to to get the defrosters and heater going. Pulling out the whole dash to repair/ replace this diverter door is out of the question until spring as this appears to be more then a one day job.

On the other hand, I am going to do what I can to fix that broken door so that it will let the defrosters/ heater work until spring.

This is one of the times that I envy you guys that have your own home shops to be able to work inside in bad weather.