Soooooooo most anyone with an E-Series where the heater air flow has needed repair too often it comes down to dealing with the vacuum reservoir and check valve so important to proper operation. The problem has always been WTF is it exactly? You can look nearly everywhere, you know its somewhere but yet its never found---until now.

My van is undergoing an engine swap so there's no better time looking for that elusive POS---sadly this is just about the only way to find and partially see this part. Even more sad is in order to R&R the existing part would require disassembling nearly the entire A/C Heating system including properly recovering the refrigerant. So without further adieu here's that F'n thing caught in its natural habitat, naked and exposed:

Inside the yellow box:




Zoomed in towards the back of the evaporator box near the metal firewall; pay attention to the yellow and red arrows:



Another same view, additional info:



The greenish lines show two gussets formed into the evaporator case---the reservoir is partially obscured by these which just adds to it being so difficult to see or find.


This is what we've been searching for, uninstalled of course:



The yellow arrow above relates to the yellow arrow in the second photo---they're pointing to the same portion of the vacuum reservoir. Note: The blue-green arrow points to what appears to be a bolt hole but its not---seems to be a flange that snaps into mating prongs on the evaporator case instead of using a threaded fastener.

The red arrow in photo #2 relates to this part, inner evaporator case:


That projection fits into the interior side of the evaporator case exiting outside the firewall--its the A/C condensate drain, this view:





Another view of the uninstalled reservoir:



The upturned flange on the opposite side ^^^ cannot be seen or felt by hand how its attached--guessing the same sort of snap-in-place fastener.


This one shows simulated vacuum tubing installed, the Ford check valve installed in what I believe would be similar to the factory installation:


Black to intake manifold, purple to dash mounted A/C system controller aka Function Control (Heat, Vent, Defrost etc)

Hopefully this shows how nearly impossible it is to access this part---it would require a complete disassembly of the A/C-Heater system inside the engine bay. I hate bashing Ford but WTF where they thinking with this idea? Did GM or Chrysler trick them into this design? I simply do not see any way possible to R&R this part any other way.

There have been a few great threads of improvised and self-fabricated vacuum reservoirs. For me its far easier buying the Ford parts and install them inside the cabin tucked up under the dashboard. Removing a few lower dashboard trim parts there's plenty of room for all this to fit neatly, cable ties holding it in place. I'll be doing that on the van shown and will probably post a different thread how that'll be done and the finished results.

I hope this is informative---I've been searching for this damn thing nigh on 10 years or so.

 

I've had a general idea of it's location but haven't seen it as clearly as you show it. Rumor has it that GM was experimenting with a machine capable of "Mind Control" for the "Military Intelligence" service of the Army.GM's technician, not knowing his wiring color codes, attached the red & black power leads to 220VAC and pressed the viewing button for Dearborn. The rest as they say was history. Ford is not to blame for this mess.

make Chrysler use left-hand threads on left side of cars....

 

Having once owned an early 60's Chrysler trying to change brakes I first bent the included lug wrench removing the lug nuts. Switched to a decent quality 4-way lug wrench and still could not budge the drivers side lugs. After a few days struggling with this, talking it over with older guys I worked with one suggested the problem lugs might be left handed--DUH!

By that time they were still on quite tight but at least turning the off the correct way got them to move. That idea never made sense but I'm still a fan of that era Chrysler products, luxo-barges that rivaled Cadillac for sheer opulence.

 

The train of thought was the direction of tire rotation would keep the threads from loosening during braking when lefthanded threads were used on the driver's side.

 

I'm sure at that time it made perfect sense logically. As we've learned since the early 60's properly torqued lug nuts regardless their twist pattern tend to stay tight no matter which direction they rotate.

 

Yes but also keep in mind that back then the front brake were drum brakes not disc which contributed to that way of thinking back then. Drum brakes have different forces and stresses applied to them versus disc brakes. To us nowadays it seems silly, but back then the use of lefthanded threads was "obvious" to them.

 

Oh heck yes----as I remember some of the designs and manufacturing processes of cars back in those days it was a very different world then.

 

I think my all time favorite bad design was the e-brake that was a drum brake built into the driveshaft. What a major safety hazard that was.

 

Seems that design is still with us on some vans or trucks though I can't recall if its Ford, GM or Chrysler who had it most recently. This might have re-emerged about the time manufacturers were having problems installing E-brakes on four-wheel disc brake vehicles.

 

The problem with that design especially in the snow is with a standard rear end if one wheel breaks traction the other side will roll. Another issue is if using it during an emergency the same opposite spin wheel forces in the back could send the vehicle into a spin on slippery surfaces. Lastly, should a u-joint snap and the driveshaft takes out the rear brake lines you also lose the e-brake.