My AC is only blowing through the defrost vent. Any ideas for me

 

Vacuum leak.

When switching to 4wd, the ESOF hubs try to lock into place. If they leak (often do), they won't engage and the HVAC switches to defrost only.

With your hood up and engine off, turn the key to Run position and listed for the vacuum pump. It should run a bit then turn off. If it keeps running, it can never build vacuum.

You can also try to switch to a different vent position after the vacuum pump stops running. See if it works and listen if the pump goes crazy, indicating a leak.

Keep it in 2wd to eliminate extra factors

Let us know what you find

 

The rubber vacuum hose that runs from the front hubs to the nipple on the frame often rots away. Good place to start your search for a vacuum leak. You can replace the hose and maintain the ESOF system or remove the hose and cap off the nipples, but then you need to switch the hubs manually.

 

Hose pinching while the system is active might isolate which vacuum line is leaking.

 

You have your answer from the above posts... vacuum leak...
Now comes the interesting part on, 'Where is it leaking?"