I had such a symptom and managed to identify the problem today. There was a hot/cold blending door or panel inside the duct whose hinge had broken. The thing was made of a single piece of plastic; more like nylon really that had been sort of perforated (long slit cuts). One side was riveted and screwed to the heat duct wall and the other side was the moving panel.

To see all that, I pulled the dash cap and the glove box, then managed to pull the vent duct (passenger side) up and out. I wanted to buy a new one but the dealers were closed today so I decided to use small brash hinges and pop rivets to fix it.

While I had everything ripped out I noticed a one inch gap between the defrost plenum and the duct that feeds it. I made an intermediate adapter (1" thick gasket out of insulation board) and now the defroster works better than it ever has.

However, as I was testing the operation through all the AC/heater control settings, I noticed that some of the settings worked great when the control was sliding from left to right and that others worked great when sliding from right to left. The vacuum control switch is the problem. I don't know what I can do about that. The part number is E1AH-190961-BA. I don't really know what this thing is called but I might try to dig into it since its goofed up. I am sure its just worn out but its worth a look.

 

My 1986 ford f-150 302 has a problem with some components missing in my dash.I need to find why the controller to the A/c defrost vent and feet it is like nothing is there when i move the controller over to the defrost area I just don't know what is missing under the dash its been that way sense i owned it like 10 years.I wouldn't know where to find the parts at.

 

Here are links to all the exploded diagrams having anything to do with the heating/AC system. Take a look at the drawings and see if it helps any.

https://www.ford-trucks.com/forums/1...ml#post9764207
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Thank you i will print those out for a reference.

 

If you look on your blower motor housing you should see two small vaccumn lines near the top. Make sure these are not broken at the top, moving on look under your dash and they should plug into a housing type setup. Make sure they are connected. My heat worked good and directions switched. I broke a line so i had to drill out the fitting pieces and push the lines in again. After I did that it worked great.

 

I am no expert by any means, but I will share what I have learned in my endeavors for better air circulation in my 1985 diesel factory A/C.

#1 = Ford blower-motors are weak and wimpy; probably the poorest blowers of all vehicle makes.

Added to that, the way that the blower is GROUNDed through speed resistors and finally weakly GROUNDed for "HI" speed, plus having much too small wire and many restrictive electrical connections, the blower-motor voltage at the motor, engine running at fast idle, fan set to HIGH, is less that 9-volts.

I added temporary jumpers at the blower, both HOT and GROUND, and that really woke things up; although not nearly so strong as a Chevy blower, it was at least twice as strong as before.


So, I spliced TWO relayed circuits into the factory wires, HOT and GROUND, that are controlled by a single SPST toggle-switch, such that I can manually kick the blower into high gear on demand.

I made my splices into the "truck" side of the blower plug/connector, so that, should I need to remove the blower for cleaning or replacement, all I need do is un-plug the connector.

Voltage at the blower now, with the relays energized, is nearly full alternator voltage = right at 14-volts.

With the A/C vents blowing on factory HIGH, I can energize the relays and the increased air movement will nearly blow my hat off.



I have another improvement in mind that I will soon employ --- a genuine Chevy blower-motor.

When I hold the Ford blower in my hand and directly connect it to a battery, the "recoil action" is akin to shooting a Daisy BB pistol.

When I do the same with the Chevy blower, felt recoil more resembles a .45-Long Colt with 22-grains of 4227.

That Chevy blower is like a cyclone.

 

It is nigh impossible to remove the cowl-cover, unless one either first removes the bottom windshield trim-strip, or removes the hood.

With either of those out of the way, the cowl-cover easily comes right off.

Of course, the antennae must be un-screwed under that little chrome cover and the wiper-arms must be removed, along with screws both under the hood and along the top.

Once the cowl-cover is off, line the under-side of all the slotted openings with good metal window-screen, stainless or aluminum.

Hot-melt glue, zip-ties, and clear silicone, all used where each works best, will hold the screening snugly against the bottom of the cowl-cover.

This will prevent further intrusion of trash and vermin.


Now, vacuum out everything you can reach down in the recesses.

Pull the blower and remove that black plastic A/C evaporator-box from under the hood; the A/C box has some screws under the hood and one or two that must be removed from the cab side of the fire-wall; nuts, I think, on the inside.


Now, you will be amazed at the amount of debris and filth that is trapped within the blower cavity and both sides of the evaporator.

No wonder it smelled like wet dogs whenever the blower was ON.

Clean it all up and spray some of that A/C foaming cleaner stuff on the evaporator --- even if the A/C is non-functional, as the air must first pass through the evaporator prior to the heater.


Access the heater-core under the glove-box and do likewise.


Remove the kick-panels, both sides, and remove the access ports you find there, plus the two ports that cover the hidden cab-mount bolts.

Vacuum all the trash that is trapped in there.


If you have never done any of this cleaning in the last 20-plus years, figure on filling a couple five-gallon buckets with all the crap you dig out.

 

Someone mentioned the vacuum control switch.

Way back in about 1987, my air circulation defaulted to DEFROST, regardless of what was selected.

I found that the plastic vacuum control switch (the thing mounted in the dash with all the control levers) was all melted, cracked, and distorted.

I replaced it with one from the auto-parts and all has been well with it since.

Way back when these trucks were new, failure of the vacuum switch was very common.

If you are having problems with air-flow, it would be worth examining the vacuum switch; as, if it leaks, it will not open/close/move the various doors as completely as it should.

Seeing as how my factory switch barely lasted two years and the parts-store replacement is still going strong, Ford must have put a bunch of cheapies in these trucks when new.

I have found the same to be true with many of my replacements; the replacements have far outlasted the originals, which shoots the "only buy FORD parts" theory plumb out of the water.

 

Hey Longrider.
Great posts, I have printed them and am going out with my 5 gallon buckets...would you please explain the splicing of relays more, I am not electrically adept and don't really understand how you are (or where you are) getting the additional voltage. When you jump the blower hot and ground, does that mean you are just bypassing the plug connector? I love the idea of having a toggle to add the voltage, please just explain what it looks like, guage wires and etc. so a dummy like me can connect it.
Thanks again for the great posts from 2007!