I just got a 2005 6L FX4 Lariat about a week ago, and the A/C was working fine. I had to turn on the defroster because it was raining and really humid, and I went to turn on the A/C the next day and it will only blow out of the defrost vents. I figured I might have pressed the wrong button on the little computer dash thing for the A/C, cause I'm used to the manual A/C switches in the xlt's. But I've pressed about every button on that thing, and it won't work.

Any ideas on what's going on? Thanks.

 

Check for a loose or broken vacuum line... Defrost is the default position when it looses vacuum...

 

Where would this vacuum line be at possibly?

 

I'm not really sure on the 05, but there is a white one on the older models that runs across the the top of the A/C box under the hood that are known to get brittle and fall apart..

 

Alright, well thanks for the info. I'll check that out, and post if this is the problem.
If anyone else has any input, happy to hear it. :d

 

On the passenger side in the engine bay near the firewall you'll see the hose that runs to your heater core. In that hose is a round black valve that sticks up with a little arm on the side which closes when the AC is on. It is accuated by a vacuum line that slides on to a nipple in the center of the valve- the ones I've seen are gray. When this line falls off, you lose AC out of the blue and then it comes back when it feels like it. My last trucks line kept falling off causing a similar issue and I had to tie wrap it in place. Good luck.

 

This is the line that seems to fall off. It is grey with a black connector.

 

Also, check the lines at the vacuum pump and the lines at the wheel hubs. If the pump is running all the time then you definitely have a vacuum leak.

 

try your 4x4 if it don't work replace 4x4 solenoid little box on passenger finder with vacuum lines going to it

 

I have a similar issue when I put mine in 4 wheel drive, it'll stay on defrost for a few seconds . Could the 4x4 solenoid be getting bad?

 

Douglas, thank you for the picture. I didn't check that spot, but I will. I also tried turning the key without starting it and turned on the A/C to see if I could hear anything under the hood working, but heard nothing.

 

Check for power and ground to the vacuum pump. If you have power and ground to the pump, but the pump isn't running, replace it.

 

I had my transfer case rebuilt. Since then when I put in 4 x 4 high the a/ c goes straight to defrost. Thought I had a vacuum leak but can't find it. Any ideas?

 

4x4 vacuum leaks are often at the hub seals. I need to replace one on the driver's side.

 

What is the degree of difficulty with tracking vacuum leaks. Is there a way to test this problem.