I have a 2005 F-250 6.0 Diesel King Ranch and the a/c ducting selection buttons quit working. Normally, I just start the a/c by pushing the "Auto" button...but yesterday, when I did that, the a/c began blowing out the defrost vents at the windshield. Once I noticed this, I pushed the button to select the split floor/face vents...but it won't switch. Further attempts to change it to any other setting don't work either.

Does anyone know whats going on with this???

 

The defrost is the default position for the system. It is vacuum operated. This usually means the vacuum solenoid is out or there is a vacuum leak.

Do you have Electronic Shift On the Fly (EFOF) 4 wheel drive? Chances are the auto-hubs are not working either.

 

Yes I do have the auto hubs...I will check to see if they are not working. If they are not working, would that indicate a vaccuum leak??

 

Are you still under warranty. My '05 was delivered just like what you are saying. Warranty repair.

 

I just verified that my auto locking hubs are NOT functioning either. Any thoughts on where to begin checking the vaccuum system??


Also, no, I'm not still under warranty.

 

I had same symptoms. Actually, my vent would shift to defrost under engine load, then back to vent... Seems that when you mash the pedal the vaccum level drops. I would have expected just the opposite, but appearently there is something else using the vacuum pressure when under load.

Anyway, mine turned out to be in the vacuum solinoid for the ESOF. It was cracked and leaking a good bit. It is under the hood. Not exactly sure where since the dealer fixed it. Shouldn't be too hard to find - just follow the vacuum lines from the hubs up.

If your vent stays on defrost all the time that might tell you something - you have a larger leak. This can be good news since the smaller ones might not be as easy to find.

If not the solinoid I know there is a bit of vacuum piping under the dash - behind the glove box.

Of course, this all assumes that you have any vacumm at all. The pump could be going or gone. I don't know if these things will run with little or no vacuum.

 

You have a vaccuum leak somewhere most likely. Any competent mechanic will be able to chase it down. My neighbor had the same problem with his 01 and I think it cost him about 80 bucks for them to find the leak and repair it.

 

Check the vacuum lines at the point where they tie into the hubs. I have had them crack twice at this point causing a vacuum leak. Just follow the lines from the vacuum pump down thru the wheel well area to were the fit onto a fitting on the inside ot the wheel area.

 

How many miles on the truck?

 

I have seen two sources for this problem.

1) Mice.

Mice lived inside the blower housing long enough to chrew through the vacuum line that passes through there.

2) Squirrel cage blower rubbed against the vacuum hose long enough to wear it through.

 

I had that problem on my 03 250. It was the solenoid on the passenger side fender wall next to the battery. It was cracked. I got a new one from the dealer for just under $40 and it took about ten minutes to replace. Good Luck!

 

Just had this problem with our Excursion 6.0 Dealer had no idea what would cause it. I finally traced it to the solenoid on the fender behind the passenger battery. I think it cost us $45 and works perfect

 

So I have a similar problem that I'm still trying to narrow down... My vacuum is working fine, and is seemingly getting good vacuum all the way to the vent actuator behind the glove box (not sure what it's actually called). The problem is, when I change from defrost to floor, it never makes it to the floor position. It can make it to the dash vents, but seems to move the lever just short of the optimum position to completely close the defrost vents and fully open the dash vents.

My question is... does this mean there is not enough vacuum (I'm not sure if the vacuum level actually determines vent position or some other mechanism?) OR does it mean a problem with the actuator OR maybe the vent lever mechanism is requiring too much force to move???

Incidentally... it seems as though, even when the dash vents are fully engaged, I'm just not getting the airflow I think I should on MAX fan... Does anyone else think the blower is weak on MAX or is it just me?

 

Just got my 06 F250 back from the dealer. Had the same exact problem. They replaced the selonoid, but the problem continued. The tech subsequently traced the problem to a pinched vacuum hose. Fortunately, it was all repaired under warranty.

 

Had this EXACT issue on my SHO. AC was blowing out the defrost. Delaer said it was fine (my LAST visit to them...). The vacuum motor/actuator thingy under the dash was bad. Proved it by pulling a vacuum on it and trying to move the actuator/hearing the leak. It will be obvious if that is the issue once you pull it. Just remember - please - verify the part is bad before you replace it...BTDT too many times.

-Dave