Any idea where this vacuum hose is supposed to be attached? It is right by the vacuum manifold by the passenger battery. My hubs weren't locking in auto so after searching on here I understood I may have a vacuum leak. I would say that I do! Can't find where to plug it into.

Update. You would think that the vacuum pump would be running constantly with a hose like this unattached but it is not. I started to wonder if I had a bad pump, but heater/defroster operation is normal. I unplugged a vacuum line from the pump with the key on and it started right up, so the pump is working fine. Maybe this hose has something to do with the locking hubs?

 

That's the vacuum line that locks in the front hubs when in 4WD. It's only active for about 30-seconds when you lock or unlock the hubs. Follow it back to the small tax/black box in the left of your picture that is the Hub solenoid. I"m guessing when you put it in 4WD you will loose vacuum and your AC will go to full defrost until the hub solenoid closes.

The hose either broke or was removed by someone. Go down to the hubs and you should be able to find the vacuum lines, follow them back till you find where the line separated or broke and you should find your culprit.

Is that an Excursion? The AC lines have tees in them that my truck doesn't, I'm guessing that's the rear AC?

 

Smashed side on the left.
Thanks for the reply. This in an Excursion 2005 Eddie Bauer so I'm guessing that you are correct and that is the rear A/C. I dug down and found a line going to the right front wheel well with a smashed end. I think it must be the one and just fell down there. The length seems right for where it would meet the other line. The end is smashed and the hose diameter is different so I think I'll try to find a coupling and see what happens.

 

That's the one
It would also t-off to the drivers side a little further down the line.

 

Update:
I got new fittings and reattached this line, but the hubs still wouldn't lock in auto mode. I used some threads on here and some YouTube videos to figure out the hub lock solenoid was bad. I got a new Dorman brand one from Amazon for $30 and it fixed it!