I was under the hood of my '94 F150 yesterday and noticed a broken vacuum line. It is the white line over by the blower motor and operates the vacuum motor on top of the heater box. The line is extremely brittle and completely broken in two. It apprears that it goes into a wire loom and disappears from there. My question is: Where does it go from there and how difficult is it to replace? I found some old links on here to vacuum diagrams but they no longer work. I think repairing this might solve my A/C problem...a/c air switches to defrost vents when engine is under a load. Has anyone had experience replacing this vacuum line? Does the new line have to go inside the wire loom? (looks like a challenge). Can you give me any helpful information on how to do it. I've never worked with/on vacuum lines before.

 

I simply patched it with 1/8" ID rubber hose. Just slit the loom back far enough to where you can get at least a half inch of rubber hose slid over the old vacuum line.

 

I did the same thing. Trimmed both ends, and used washer tubing.

 

The hose goes through the firewall into a junction behind the glove box and into the dash control switch for youre heater/ac, etc. I had the same problem with a brittle worn away hose on my F250 in the exact same place as yours.

Here's what you do to fix it. Don't replace the whole line, just a part of it. There should be a whole group of hoses taped up in a split loom there. Carefully cut the split loom tape away and expose the hose as far back as you need to until you get to a point that is viable for a splice on your broken hose. Should be a couple inches past where the tape/split loom ends. Once you're there, cut off the old, nasty white hose so you have a good end to splice to.

I searched all over town for the correct hose and splicer but finally found what I needed at NAPA. It helps if you take a piece of the old hose in there so you can show them exactly what you need. Nobody I found carries that same hose, even the dealer, but NAPA had something close enough. I needed less than a foot. The dealership called it spaghetti hose, btw.

Pop the old white hose out of the black rubber connector on the vacuum solonoid, plug your new hose in there and then splice it to the white end under the split loom and you should be G2G.

When you start it up, don't get in the truck. Reach through the window and do it so you can watch to see the solonoid do it's thing. Should work just fine for you.

 

Had the same problem! All was needed was to replace that brittle white line...Everyones suggestions are a fix!

Learned that here, BTW!

 

Just to add a pic for this common issue....

 

Great info! How exactly do you make the splice between the old and new hose?

 

The white hose outside diameter is the same as the inside diameter of the windshield washer hose. (That I used.) Cut about 1-1/2 of the WW hose, black, push one end white in one side, the other in the other end, grab a beer and you're done. No massive pressure/vacuum so no clamps, etc.

 

Yeah.. what is that valve? Mine isnt hooked up. The vacuum line was just as brittle as 94 Mesquite mentioned. Just curious........

 

Advance Auto had what they called a "vacuum splice" in (oddly enough) their vacuum repair section. I imagine just about any good auto parts store may have one on the shelf. It's just a package with a three inch long piece of rubber that you plug each end of the hose in to repair a break. It was about $2. I plugged the 12 inch replacement hose that I found at NAPA in one end of the splice, the remaining white tube in the other. It was a tight fit, but I guess it's supposed to be. I checked the operation of the thing just today to make sure it was still working correctly and it is. It's been about a month or so now, so I guess it holds pretty well. If I get a minute this weekend I will take a photo and post it.

I started to try the fix that skaterbro talks about with the 1/8" ID hose, but I could not find any that was perfectly round on the inside, so I figured it would leak. Good idea, though, if you can find the right stuff to make it work. This "vacuum splice" worked perfectly.

 

Not totally sure yet what effect it has on the inside of the truck, but I have checked what positions the valve is in with corresponding switch positions.

With the dash switch on Max A/C or Floor, the valve is actuated. All other switch positions, the valve is not.

 

Oh, well it has no effect on me then. (A/C torn out). Good luck to anybody else that needs it though. This thread seems to be pretty helpful. Everyone is in agreement with the fix.

 

What I did is cut the loom back far enough to replace what was bad. I also slid a piece of heater hose slit down the side over the loom to protect it from the heat from the heater hoses. I think this is a major factor for why these particular hoses rot out so often.

And yes, fixing that line will fix your AC problem, I had the same problem and repairing that rotted out line fixed it.

 

What I did is cut the loom back far enough to replace what was bad. I also slid a piece of heater hose slit down the side over the loom to protect it from the heat from the heater hoses. I think this is a major factor for why these particular hoses rot out so often.

And yes, fixing that line will fix your AC problem, I had the same problem and repairing that rotted out line fixed it.

 

The vacuum actuator (motor) that you see operates the blend door.
Even if you have no A/C you should still have a control for outside air/heat