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I have a 2000 F-350 with the V10. I have read a few threads about the vacuum leaks affecting these trucks, and I've run into the same issue. On the passenger and drivers side where the vacuum line connects for the Auto Lock Hubs, the lines were disconnected at the back of the hub and dangling. I am also experiencing defrost on all modes whenever I use the AC. This truck has 152k, is there a specific place I should look for different leaks in the vacuum system? Somewhere that tends to fail or wear? And what exactly do I need to do to replace the worn lines that go to my hubs? Thanks to anyone who can assist, I hope I didn't overlook the answer somewhere else. I'm also wondering if my Cruise Control failing to engage could be connected?
Have the dangling vacuum lines that used to go to the hubs actually been plugged at their ends? If not, there's your leak, and that's why your AC only works in the default defrost mode. A couple of old golf tees and some tape will plug them quite nicely.
Yes vacuum leaks will cause your air to revert to the defrost position. If both vacuum lines to the hubs are removed it is most likely the problem. You can do 2 things. 1) remove the lines and plug off the connection. You can do this to see if the air then works other then in the defrost position. 2) You can just go to the parts store and get some vacuum line and replace the bad section from the hubs and trace it to where they are plugged in.
If both lines were removed that tells me their might be a issue with your hubs.
As far as the lines being off I don't see how that would prevent your cruise control from working. That is something that I don't know how to fix or trouble shoot.
I will go get a couple of caps for those vacuum lines in the morning and see what that does. I honestly prefer to lock the hubs manually, so I'd probably end up just leaving them plugged if that's the leak
Cap off the line going to the PVH solenoid to eliminate the whole subsystem from the vacuum circuit. If the climate control now works properly, either the PVH solenoid is bad (leaks) or there is some other leak in that system. The lines to the hubs only get vacuum when the PVH solenoid is energized, so the disconnected lines are a by-product of someone's ineffective troubleshooting, they're not the cause of your initial concern.
The Speed Control issue s separate. Start by checking the SCDS pressure switch and its related recall harness on the master cylinder, it's the most common failure. If you recently acquired this truck, you'd best check to see if recall 05S28 was ever done on it.