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So I'm doing a little deer scouting today and I have the AC in auto mode at 74. The truck is a 2006 350 6.0 if it matters. I came to a bit of a soft spot on the edge of the timber so threw it into 4 high. Lockouts are in auto position. About 5-10 seconds later, the air stops blowing out of the main dash vents and changes to the defrost vents. Can anyone help me with why that would happen. About 30 seconds after I went back to 2x, it came back to the main vents again. Is my truck possessed?
Nope. You have a vacuum leak in the ESOF (I assume you have it). I would start by putting a vacuum on the lines going to the reservoir. If it holds then move down to the steering knuckles and see if vacuum holds there.
Thank you. Is that a pretty easy test? Does there happen to be a write up for it? I'm rather new at trouble shooting (I'm not even sure what the ESOF is...haha). Should I just take it in and tell them the above?
ESOF = Electronic Shift On the Fly (auto locking hubs)
If the hub seals are leaking, it could get to be a pretty involved project if you aren't mechanically inclined. You may want to consider taking it to the dealer. But, you can save a LOT of money if you can do it yourself.
If it's just a vacuum line leak, it may take a little time to find it, but it'll be easy to fix.