Where is this little black vacume hose between the battery and firewall? Does it pass through the fire wall? Do i need to remove battery to find it?
I cant seem to find it. Does anyone Have a picture?
i Have a 2000 f150 xl. where is the vacume pump also.

 

You don't have a vacuum pump. Only diesels need them.

 

Okay then.... why would my vents not be switching?

 

You vacuum is drawn from the engine. Does it not switch at all or does it switch back and forth as you accelerate? If it goes from defrost to vent or floor you just have a vacuum leak in a line. If it doesn't switch at all it could be a vacuum motor.
This is the climate control schematic for my 98, your is probably the same. I don't have an actual picture of it going through the firewall.

 

It does not move at all, where is this vacume motor located, and how, if any, way can i test it?

 

Focus on the vacuum supply represented by items 12, 13, 14, & 15 int he vacuum schematic.

Look between the battery and the firewall for the black hose that passes through the firewall. It's easy to find... and is the most common failure.

Steve

 

It is a small, hard plastic vacuum line about 1/8" diameter. Yor will have to look for the crack. You need to start looking at the firewall.

 

I have an 01 5.4 SCrew so this may help out... I just fixed mine with the help of this thread. My problem was the vents switching back and forth from vents to defrost upone acceleration.

Location; between the battery and the firewall as others have mentioned. Look for a 'T' with three lines running to them it is hidden fairly well under/near the electrical distribution area. There will be a check valve of sorts and one side of the tee should be a traditional vacuum hose (the part of the 'T' going towards the driver side, on one of the other two sides of the 'T' will be the 1/8" round plastic tubing. It is fairly easy to trace the one going to the firewall. Just like the others on this thread said it was cracked right there! I had stopped by the auto parts store prior and bought a couple of different sizes of the vacuum hose/tubing and did a splice repair. I cut a 1" piece of the hard plastic vacuum hose that had deterorated and put a 4" piece of hose over both ends so it would have some support and strength. I then double zip tied both ends of the hose and everything is perfect. Vents work like they are supposed to.

It may have to do with rubbing against the battery or maybe over the years the battery acid 'gets to it'. You do not need to remove the battery to fix this (if this is indeed your problem). Repair time included 10 minutes to track down the line and 5 minutes for the fix. I have pics but I do not have access to post.

BTW, many thanks to all that have posted on this fix!