Hi guys and gals,
I've got a new toy, an 89 F150 with the 351W, FI. I'm having a lot of trouble getting good diagrams for the vacuum routing, and i've still got some questions left.
Ideally, someone with the same engine/configuration could post a picture of their correctly working setup, and I can just copy that.
Specific current questions:
The "Coffee can" on the passenger side wheelwell is a vacuum reservoir can, and that's supposed to keep the HVAC system from losing vacuum under heavy engine load, right?
The small box protruding from the A/C and Heater area in the back passenger corner of the engine compartment; what is it for, and where is the vacuum line from it supposed to connect to?

 

You'll find most of your vacuum lines here:Replace Plastic Vacuum Hoses with Rubber - FSB Forums

 

I've seen that thread before, and while it's got a lot of useful information, it doesn't cover some of the pressing questions I have.

Let's start with this one:
The small box on the outside of the HVAC box in the back passenger corner; mine has a vacuum nipple, but isn't connected to anything, and I can't figure out where it's supposed to connect to. I also have very little heat coming out, but my radiator is full, and everything else HVAC wise works correctly.

 

No that is not right. The passenger side wheel well vacuum reservoir can is for the emissions system and has nothing to do with the HVAC system.

That is your vacuum reservoir tank for the HVAC system.


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Thanks for the diagram, it's quite helpful!
I think I might be missing a "tee". I've added some photos, what do you think is missing?





Close up of the HVAC stuff.

 

In your last photo, in the upper left corner is your vacuum control valve. This is the vacuum for your blender door for heat and A/C.

 

Maybe this link will help for the blender door vacuum:Vents are dead - FSB Forums

 

Yes the "T"/check valve.

Wrong, that is the outside/recirculate air door vacuum motor.

That link is also wrong. The blender door is cable controlled and not vacuum controlled.
Also the blender door is 100% inside the cab and no part of it is inside the engine compartment.

 

This is fantastic, thanks!
Do I need a specific tee and check valve, or will an off the shelf part work?

 

Not sure if this is of any use to you or is even applicable, but here is the vacuum diagram for the 5.8l off off my 1994 f150.




Vacuum Diagram 1994 F150 5.8l

 

There are no vacuum lines for the HVAC system in that diagram.
That diagram is for the emissions system only.

 

Subford,
Would you please send me the other vacuum pages (140-1,140-2), or tell me which manual you have?
Also, does anyone know the part number for the small check valve and splitter in the diagram?

 

140-2 is a vacuum diagram of truck with a Diesel engine.

140-1:


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Thanks!
Now if I just can just find that check valve/splitter, i'll be in business!

 

New news!
So, I installed a motorcraft YG193 vacuum valve that I found on Amazon ( ), as shown in the pictures below. So far, no difference, but i'm waiting to test the A/C under load. I still don't have much heat coming out, and now I see that when I move the selector from hot to cold, the vacuum operated damper motor, located on the shroud at the passenger firewall, doesn't move, which I expected it to.
Thanks to a recent blowout on the front right wheel, I have some new damage to the blower motor shroud, so i'll be working on that next.
My next round of questions for you:

1)What else could I be checking to determine why i'm able to get great A/C, but really poor heat on any setting (vent, floor, defrost)?