I had the A/C running on my Ex and switched to 4x4 and it went to defrost then after about 2-5 min it switched back to A/C, is this normal or do I have a vaccum leak somewhere and where do I start to look for the problem. I tried it 3 times and did it all 3 times.

 

There is a connector behind the glove box. Check for a vacuum leak there. Next place is your hubs.

 

Sounds like a vacuum leak to me. I would start by ckecking the rubber lines going to the hubs they're notorious for cracking and causing a vacuum leak

 

I replaced each of my wheel-well vacuum hoses with 22-1/2 inches of 3/16" (4.8mm) SAE 30R7 fuel hose each side. Secured the ends with a tie-wrap.

It should last a lot longer than OEM, and it fits perfectly.

Pop

 

The other thing is to make sure your vac pump is actually working, mine did a similar thing and after replacing the pump it worked perfect.