Vacuum leak - usual suspects?

I have a small vacuum leak evidenced by the hvac outlet switching from vent to floor under load. Are there typical problem areas to look at first?

Get a can of carb cleaner and spray around the vacuum hoses with the engine running. when you hear the RPM's increase you will have found the leak
Check behind the battery and behind the throttle body areas, and all other vacuum hoses

Yeah, I know that procedure. I've had mixed success with that in the past, especially with small leaks in out of the way places. Was just wondering if there are common places to look first on the 5.4 motor.

I just put a nav system in my 97 expy. While I had that apart I noticed vacuum hoses on the back of the hvac controller switches on the dash.

Check the small vacuum lines right before they go into the firewall to your controls. Had the same problem with vents changing and that's where the leak was, bend the lines a little and visually inspect each one, mi e was cracked just enough to cause the problem but wasn't obvious at first look.

I had the same problem but that hose was broken open as it gets old and brittle. Cut off the bad section and get some 1/4" gas line from the hardware store....or take a piece of the cut off line with you and make sure it fits inside the gas line. I used it to replace that section and everything inside starts to work. Apparently vacuum is what Ford uses to control all the A/C heater vents and flaps.

Hey I'm having an issue with the vents in the front panel of my 00 expedition. When i turn on the blower, it all goes into the defrost location vents. From every switch i turn to "panel" to "ac max" to floor" and it'll keep blowing from the defrost vent. I dont have an owners manual so finding switch fuse will be very difficult. I'm fine when I'm alone driving because I can just use front and rear ac to cool me off but with passengers in the front... It gets a little too warm. It could be some vacuum lines from the switch or it could be some fuses that could be blown. So far i don't have any check engine or anything light up in my cluster so i really don't know. I might take it to a mechanic it anything, but if it's something i could fix on my own, please be kind and let me know. Thank you guys!!

You will spend less and learn more by getting you own smoke machine for the job.

Vacuum leak check vacuum line behind the battery