cruise control

my 99 laramie slt dually w/ a turbo cummins diesel has the buttons for cruise control on the steering whl but i have been unable to get it to work while driving & can't seem to find a fuse or relay for it in the
wiring diag can someone give me a clue . because the buttons r there i assume it was installed but is that correct / help me find a clue or a possible fix for this .... thanks in advance.... lost in the desert out west
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When you hit the 'ON' button, does the Cruise Control indicator on the instrument panel come on? Does the horn work? If no to both, I'd suspect a bad/damaged clockspring in the steering wheel.
If the cruise indicator comes on, but just won't activate, I'd suspect a problem with the cruise control servo or cable. Check the cable between the cruise control servo (should be under the driver's side battery tray) and the APPS module. Make sure it's not busted. Then check the vacuum lines between the cruise servo and the vacuum pump, on the back side of the power steering pump. You need vacuum to actuate the cruise control. (This is all assuming you have an automatic transimssion... manuals handle the cruise control differently).
Another possibility is a faulty brake pedal switch... if the computer thinks the brake pedal is depressed, cruise cannot activate.
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