E-Series Duct Control & Operation

This is a brief presentation of the components and operation of the vacuum controlled air flow through the ducts. Created with E-Series from 1997 to at least 2008 in mind. It may transfer to other years and Series Ford vehicles as well however there are no guarantees.



^^^^ Vacuum routing schematic for the system, note the hose colors and solenoid numbering that correspond to the above schematic and these points as well:

*Vacuum Solenoid #2A is only present if factory rear A/C is installed; it is physically located on the rear A/C case. For this presentation it is not addressed, mentioned only to identify its function and location since its part of this schematic.

• **Vacuum Solenoid #3 Re-circulation door used only in Max A/C, physically located below dashboard passenger side near floor near fuel inertia switch.

Note 3 above refers to vacuum lines as they're typically physically found on most E-Series vans. Red line is from intake, the junction shown is under the hood just above the oil fill tube on gasoline engines; diesel engines should be in the same approximate location. This line connects to the portion of of the vacuum control system that is in front of the firewall but nearly impossible to access with engine installed.

Actual locations of the vacuum solenoids

Top center of dash under removable access cover:



Below dash near fuel inertia cut off switch:


These two videos show the vacuum solenoids moving relative to the Function Control Switch:

You Tube

Please note the recirculating door appears to be "open" only when Maximum A/C is commanded. At any other setting of the Function Control or during complete loss of vacuum in the reservoir it will appear to be "closed". This is because when its "closed" air flows from the outside inlet through the heater or evaporator core and then into the ducts.

When Maximum A/C is engaged it will "open" which diverts air flow from the outside inlet to air inside the cabin being drawn in and through the heater & evaporator core. In theory this allows for already-cooled and conditioned air to not be drawn in from the outside which would be at a higher temperature and humidity level than that inside the cabin.

Another part of this control system is the vacuum reservoir located as shown in these views:




Zoomed in for closer view:




As installed during original build the vacuum reservoir is nearly impossible to access for service or replacement due its location under the Heater Core/Evaporator case. Held in place by two fasteners where one is between the far right side of the case and the inner fender, the opposite side partially visible here:




If it becomes necessary to replace the vacuum reservoir and/or check valve it can be easily relocated inside the cabin mounted securely out of sight with full function of the vacuum system maintained. Here's one suggestion or how to:

Step One remove this trim panel:




Step Two remove this metal plate, held with (4) 8MM head bolts:




With access now available you can install a replacement vacuum reservoir similar to this:



Yellow arrows above point to this 10MM headed bolt:



Using original factory hard vacuum line under the hood from intake splice new hose here:


Red = Original line from intake
Yellow = New hose to cabin
Green = Original line to original vacuum reservoir, remove or leave unconnected but secured so its not left loose.


Route a new vacuum line through one of the heater coil tube holes in the firewall---they tend to be loose-fitting enough for a hose to poke through inside the cabin.

This photo shows that to a degree--tough angle to photograph properly:




Perhaps a better view how a replacement hose can be added by pushing it through the firewall hole where the heater core tube protrudes into the engine bay:



Showing the assembled factory parts as inserted into the system before mounting the vacuum reservoir to the dashboard superstructure:




Ford Part Numbers for above:

Vacuum Reservoir: YC2Z-19A566-AA
Check Valve: D70Z-19A563-A or Motorcraft YG-193
Hose: Any higher quality 5/32" ID tubing such as used for windshield washer solution. (I show silicone tubing as it was handy at the time of this repair.)

I also use Dorman #47380 Vacuum Connector Pack which has enough hose/tubing connectors to do this job easily.

Please note: when this relocation is complete there's no need to worry about the original vacuum reservoir or any of its attached parts--its simply too difficult to access anyway, just leave it all in its original place. If it were easier to replace we'd not have to relocate it for future servicing---it'll do no harm or cause any problems if not removed.

I'll post a follow up thread to this showing actual photos of the electro-vacuum switches mounted to the dash board aka Function Control.

This ends Part 1---Part 2 is now posted.

 

Lots of great information here, added to tech folder!

 

E-Series Vacuum Control & Operation Part 2


As in Part 1 this applies mostly to 1997 through 2008--it might be helpful to other model years however that range surrounds my direct and hands-on experience.

Please note once again I strongly recommended having an EVTM for your particular year as a wiring reference for wiring circuits and colors---those shown here are NOT used for all years, shown only for illustration purposes

In this part we will occasionally refer to the Vacuum Diagram also shown in Part 1. Colors and device descriptions added by me--this version does not exist outside this thread:



Note 3 above ^^^ refers to vacuum lines as they're typically found on most E-Series. Red line is from intake, the junction shown is under the hood just above the oil fill tube on gasoline engines; should be in same approximate location on a diesel engine as well. This line connects to the portion of the vacuum control system that is in front of the firewall but mostly out of sight and practically inaccessible, tucked under the evaporator case--can be seen in Part 1. This photo shows the physical connections shown in the above vacuum diagram:


Lines in this image are the same colors as shown in the vacuum diagram however the junction between the red and black lines has been disconnected in order to run a new line bypassing the factory installed reservoir and check valve (orange hose); in this instance ignore the orange line.

In this Part 2 we're mainly addressing the dash-mounted electro-vacuum control sub-assembly which includes the function control selector along with blower speed controls--illumination is integrated into the assembly. There are three versions, shown as follows:

First is standard without rear A/C or heat:



Variation #2 with rear A/C and heat:



Variation #3 with rear heat and A/C and added rear control selection:


Note 1: Variation #3 ^^ was installed on vans with full headliner that also had rear heat & A/C as added options. The rear blower fan speed could be controlled from the passenger seating area behind the front seats. Once the REAR CTRL selection on the front module was made passengers could control the fan speed. If this version was not set to REAR CTRL the rear control would not affect the rear blower speed. In that condition rear blower speed could only be adjusted from the front seats.

Note 2: Temperature of the rear A/C or heating can not be raised or lowered as it can in the front. Only varying the blower speed can the sensible temperature of the rear seating area be changed suit passengers.

Showing the back side of dash mounted control fully populated with component identification:


Showing individual switch chassis wiring harness connectors to help identify wire colors as might be shown in the year appropriate EVTM:

Front Blower Speed:




Rear Blower Speed with REAR CTRL feature (Red/WH wire):




Temperature Control wiring harness connector:



Illumination wiring harness connector, wire colors typically Black & Blue/Rd:



Once again please refer to your year E-Series EVTM for exact wire colors; those shown here may not be the same as yours!

The actual Function Control Selector is an electro-vacuum device combining electrical switching and vacuum signal routing through the different circuits and solenoids associated with air flow. Here it is:


Vacuum harness complete:


Connection end to device:


Connection end to FCCB:


The Vacuum Harness connects to the vacuum solenoids here:



Referring back to the Vacuum Diagram follow the light blue lines to see how the vacuum is routed and/or changed via the Function Control Selector:



So this concludes my input on the vacuum controls and devices as found in E-Series vans---I hope it's helpful.

 

I gotta get back at mine, I used a small check valve, put it in the doghouse by where I connected my line, it's failed, wont hold vacuum, I think I'll run a line inside, and use a check valve like yours.

 

Interesting to see that i have Variation #3 with rear ac and rear control.
I do have ac in the rear but it does not have any heating, only ice cold air out in the back even when the front is on full heat and hot air is coming out the ac vents.
Also i don't have any switches in the rear for rear control? Could that be the reason for the rear ac not delivering heat ( maybe un-connected wires in the back seat wall, just hanging loose in there).

This was a real nice decription of the system, just what i was looking for.
I think i will have to order a blend door actuator, just in case (although it takes several weeks to get here, usually 4-6 weeks).

Is there a way to stop the blend motor from moving until i have a new one at hand? Like locking it in full open blowing out the dash position?

 

The blend door is used only to control the air flow's temperature---it moves to modulate outside colder air as it flows across the heater core. With it wide open the air will be whatever ambient temperature is---that would be the lower or "cold" setting on the dash mounted Temperature control. When that is set to "hot" the blend door closes so the air flow is heated by the heater core. Moving the Temperature control somewhere between the extremes opens the blend door so incoming air is "blended" with the heater core hot air to modulate the interior temperature. When you're in A/C mode the same thing happens, air flow is affected while the evaporator remains at a constant "cool" temperature.

The air flow is directed by the Function Control switch (Heat, Vent, Defrost etc etc) which doesn't involve the blend door at all.

When you get time post a photo of your heater & A/C control located center of the dash board just above the radio.

 

This is the heater controls that i have.


And in the rear, only AC inside the wall, with vent outlets along left sidewall.


So, according to your vacuum control diagram i have vacuum solenoid #2A as well.

I think connecting a vacuum gauge in the center of my dash is the next step, just to be sure that i still have a good vacuum when the air stops coming out the vents.
Should i tap into the white tube going to the connector in the centre of dash inspection cover?

I had 27inHg vacuum at idle when cold engine.
Also my vacuum pump is making a lot of noise, sounds like an exhaust leak ticking sound. Thought it was a leak in the exhaust manifold at first.

 

You have the typical Ford heater controls----the schematic I show in this thread is what you have, there's nothing different or special UNLESS someone has been mucking about with that system.

I'm not sure you have a Ford factory rear system as your van appears to have been converted by someone. If that's the case I will know absolutely nothing about that part of your van.


Your system is shown schematically at the beginning of this thread---there are no addictions, options or other changes Ford offered since at least 1997.

Following the vacuum diagram included at the beginning of this thread shows a black line that feeds all parts of the vacuum heater system. The white line is for the air recirculating door. Typically the line feeding the Black link at point X will be red---that's listed as "from intake" if you have a gasoline engine. Regardless the vacuum source should be a red line.

That's a great Hg value---the ticking sound of the vacuum pump could be your issue. Connecting to the black line under the inspection cover will show if you loose vacuum along the way. If you discover a loss of vacuum the next step would be connecting the vacuum gauge close to the output of the vacuum pump to see if that's the culprit.

I have no clue how diesel engines work nor their components but from what you're describing the vacuum pump might lose some capacity when it gets warm. I don't know.

One other think I'll offer politely---when you quote something in a lengthy photo-rich post like this edit out the images not pertinent to any question you might have. This thread is already very long so repeating the same photos etc makes it unnecessarily more lengthy.

 

I found this on YouTube and thought it would be helpful:

 

Not a thing there I didn't cover in what I originally posted!

 

I totally agree, and not to take away from your excellent work. Some people learn better from videos… like me 😉

 

I did all of this only for the check valve that I added to fail, I really hate this stupid crap in this van.

 

The newly added check valve failed? If so what brand was it, did you install it in an easily accessible spot?

 

JWA where is the factory check valve? Mounted on the reservoir?

 

Typically, yes. I've never seen it in place because its under the heater core case between the inner fender and the case itself. This is basically confirmed since it can't be seen anywhere inside the cabin.