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Yesterday, I crcnked up my EX, and I had the A/C set for normal air conditioning, and I noticed that it was blowing like I had it on defrost . I switched it to MAX and it did the same thing. I was getting PO'd, but I went on to church and left it on the MAX setting. When I got back in the truck at noon, I cranked it up and it worked fine. Still working fie today.
The little hoses that go to the backside of the front hubs are a common place they begin to leak.
There's a couple of o-rings that are involved, too. One is around the hub locking assembly, and is accessed by removing a snap ring. The other is buried deep inside the hub, and is normally serviced only when the hub is removed for needle-bearing greasing.
It is (likely) a vacuum leak issue. Vacuum is used to control the dampers for the HVAC system as well as the auto locking hubs. Or at least that is how I'm reading these other posts. I have no experience on solving this one, although mine does the same thing, with heat, AC..., it regularly switches to the defrost vents.
Yes if they're not working and your A/C controls aren't working then sounds like you got a vacuum leak. I'd start at the pump and tank and verify it's working. Then start from there working out to find the source.
Is that a statement or a question? If a question, the yes - sort of.
It would be similar to say the truck is "controled" by the steering wheel. While the statement is true, it is not complete. It is also controled by the brake pedal, the accelerator, the gear shifter...
In the same way, the 4wd is (in part) controled by vacuum - to actuate the auto locking hubs.
SO if I cannot get my auto manual locking hubs to move, then it is a vacuum leak. Right?
John
By hand, you mean? If so, then no. Just because you cannot turn them does not signal a vacuum leak.
There are vacuum lines under the glovebox that can come loose plus the vacuum "pump" is under the hood. I wish I could take pictures for you but I have a 2WD this time around. Maybe a search in the SD or this forum will turn up some more info. It is reasonably common enough that it has been discussed before.