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Hi, I’m working on a friend’s 2005 F250 6.0. While I have it he wanted me to check out his ac system. What’s happening is no matter what he sets it on, the air is directed out of the defrost vents. I’m aware of the vacuum leak issue about the ac going to defrost when shift on the fly 4x4 is used, but his is stuck on defrost the whole time. I haven’t heard of this before. Oh, and it’s a manual ac. Any advice? Thanks!
If you have a vacuum leak it will default to defrost. You can by-pass the ESOF and verify where you have a leak. The blue line in the pic below is to the HVAC vacuum line. Jump it straight to the vacuum pump and verify HVAC operation. If it works you have a leak somewhere in the ESOF system. If not you have a leak somewhere in HVAC system and possibly the ESOF system as well.
