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Vacuum diagram for on ford van?

In the rear there are two actuators, one inside the passenger compartment, next to the middle seat... it is attached to a blue lever. It is vacuum actuated with a thin white vacuum line. It gets its vacuum from the switch on the dash. I'll cover that in a llittle bit. The blue lever when in the down position will direct air through the roof vents, when in the up position it will direct air through the side bottom vent. That acutator is spring loaded, and when there is no vacuum supplied, or insufficient vacuum supplied the default position is with the lever in the up position (air flow directed to the floor).

There is also another actuator on the driver's side under the truck that is a vacuum controlled valve. It controls the flow of hot water in and out of the rear heater core. It gets is vacuum supply from the same vacuum line as the inside the car actuator. One line comes from the switch in the dash and is later split to feed both actuators.

On the right side of the dash there is a switch that controls the fan speed, and whether one will get AC or heat in the rear. That is an interesting switch in that it is a vacuum switch, and an electrical switch in one. It has a black vacuum hose supply line, and a white vacuum hose that is affected by the flipping of the switch to determine if the white vacuum hose will have vacuum. That is the white vacuum hose that controls the rear two actuators I mentioned above. It is also an electrical switch that determines the rear fan speed.

Here are some of the steps I took to determine that problem is a switch that is leaking vacuum.


There are four screws that holds the switch panel in place.
And one that holds the right hand switch in place.
The black hose in the back of the switch brings vacuum in, and when the switch is turned to heat, it just blocks the hose so that there is no vacuum leak. When the switch is turned to rear AC, it connects the black and white so that the white has vacuum (which shuts the hot water off from underneath, and flips the blue lever on the inside to direct the air to the roof.)

Check vacuum at the black hose at the switch and have vacuum. So you know that I was loosing some vacuum between there and the actuators.

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See the diagram below :---

I would suggest tracing the blue vacuum hose from the switch to the actuator and first check to make sure there is vacuum on the blue hose, if not then the mode switch is likely bad or the hose has a leak from the switch to the actuator, if there is vacuum then the actuator likely is bad.

i have included the vacuum diagram for you to help you familiarise with the system


see the blue hose in the second image:---

graphic

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graphic
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