Posted on the Excursion page - - but thought I'd ask the 7.3 crowd too.

I think I need a new vacuum harness ... the one that connects to the damper door selector switch (part YH-1450 - changes from floor to defrost, to vent, etc...). Anyone know the part number of a vacuum harness, and/or where to buy (connects to the back of the switch)?

And here's why I feel like it's the "fit" of the vacuum harness. I've tried a couple of new damper selector switches but still get a leak when in the "off" position. However, if I take the harness loose and hold my thumb over the vacuum holes, then the vacuum pump will shut off ... otherwise pump continues to run. Pump also shuts off with selector in positions other than "off". One other piece of info, Max AC doesn't work properly (diminished air flow through vents and some through the defrost).

Ideas and solutions, or where to buy the vacuum harness? Thanks!

 

I know virtually nothing about the vacuum system, but can offer a suggestion about the MAX-AC problem:

On occasion a flimsy plastic "baggie" will get sucked up into the air box's cabin air intake. You can easily look up inside there to see.

This happened to me, and surprisingly after mentioning this to others, sometimes it's their fix, too.

Pop

 

Is this what you're looking for? Part #14401

http://www.fordparts.com/Commerce/Ca...o=14401#Search

There are several variants depending on your specific engine..
Seems expensive

 

Pop,
thanks for the suggestion - - I have 3 kids and will definately check for the baggie

 

MalwareDray,
thanks for the link, but that appears to be the wiring harness, not vacuum. The blender control (far right and changes where the air blows ... vent, defrost, floor, etc...) has an electrical connection and vacuum connection.

So, when the vacuum connection leaks, the vacuum pump runs continually. It also runs longer on start-up since the reservoir has bled-off.

I appreciate all the input and will certainly look into all ideas.
Duster

 

Yeah I don't know then.
Couldn't find any diagrams with it shown.
is it just a hose? If it is, usually you can just go to the parts store and pick one up by the foot. I don't think Ford sells them parted out. Could be wrong though

Sent from my Galaxy Note 3 using IB AutoGroup

 

Actually several hoses that go into a small flexible plastic block. The block snaps onto the rear of the damper switch.

It looks like a two of the lines are vacuum entry and return lines, then the other lines redirect the vacuum pulse to initiate operation of dampers that then change where the air is directed to flow. I'm pretty sure mines leaking from where the small plastic block connects the vacuum entry (black hose) to the damper switch.

Maybe i'm using the wrong terminology? I'm sure you'd call the collective wiring a wiring harness. Is it correct to then call the collection of vacuum lines a vacuum harness?

 

Does this help?

 

Rich - - have always enjoyed reading your posts, very informative.... including the most recent about powering-down the compressor .. I'm staying tuned for your results.

Thanks for the diagram. Part 16 (AC/Heater function selector switch) doesn't have individual vacuum lines connected, rather each vacuum line goes into a flexible/soft plastic block, that then connects to the function selector switch.

When I have the soft plastic block off and cover the holes with my thumb, the vacuum pump cycles off ... as it should. When connected to the function selector switch, and in the off position, vacuum continues to bleed-off and the vacuum pump will run. So, I believe it's where the soft block connects to pin 3 on the selector switch that I've got a leak. (as an aside, i know my hubs leak, so I recently disconnected and plugged at the PVH solenoid)

I'm beginning to think that the soft plastic block has lost some of it's flexibility over time (hardened) and thus has started leaking instead of seating properly. I'd like a new harness, but another option is to cut the lines and connect each line to the appropriate position on back of the switch?

Still pondering solutions - - besides replacing pump after pump when they burn out

 

Lots of good info just hit the other thread you mentioned.

If this were going on in Stinky, I would grab my Mity Vac with a vacuum gauge and start testing each of the components. This is how I found about 4 vacuum leaks in the first two years of owning the truck. This is also how I tested my fuel line assemblies before final installation. I can't stress enough how useful a Mity Vac with a gauge is on our vehicles.

 

Thanks for the diagram!

I may get a Mity Vac ... but I think I can hear the leak at the connector. Thought about cutting vacuum hoses and connecting them directly to the back of the switch, but am unsure I'll get a snug fit hose-to-switch. So, I guess I need to go by the Stealership to ask about replacing the vacuum harness.... but first I'll do a little search for a Mity Vac. Sounds like a tool that will get some use.

Thanks!