I just replaced all my vacuum lines, check valve and reservoir last year and everything was working fine. I just got back from a trip and the cruise was not working and my vents were acting crazy like they did before. Visual inspection doesn't show any issues with the lines and the cable seems fine too. What else can it be other than vacuum lines?

 

The buttons are on the steering wheel? I would guess a switch or the clock spring. Did you check power and ground?

 

What year truck and what drivetrain? I'd highly suspect another vacuum line is broken that you might have missed, but it could also be what Master Tech mentioned, possibly depending upon the year of the truck.

 

Sorry, it's a 2001 1500 3.9l 2wd automatic trans. I'm guessing it's a vacuum leak but like I said, it passes visual inspection, haven't been able to do more than look at this point. What's this about a clock spring? Yes the buttons are on the steering wheel and the light comes on.

 

The cruise servo is under the battery, and takes some abuse from it's location. It is vacuum powered, so, if it fails, you get a vacuum leak.

 

I replaced the servo last time as well, not sure that anything was actually wrong with it tho.

 

Only one check valve? What did you replace it with? You should have two check valves one next to the intake and another one up near where the vac line goes into the firewall. Another thing you need to make sure you install them the correct way(vacuum flow direction).

 

I replaced the check valve near the intake manifold and the reservoir near the windshield with the big round GM ones, it worked great until recently.

 

Did you check the vacuum line going to the cruise control servo? That line is somewhat hidden and a good leak candidate.

 

Sorry, I misread your post. Apparently my visual inspection was lacking. I went out just now and put my hands on the rubber connector to the servo, of course it was bad. Fortunately I had spare connectors in the glovebox, I haven't road tested it yet but I'm betting it's fixed.

Edit: Yup, that was it, should have looked there to begin with, it's not the first time I've replaced that particular connector.