2002 dodge ram 1500 4.7 Quad cab 4×4

The cruise has not worked since l purchased the truck in 2013. The green cruise light would come on for a second (while driving) then go out and not come back on till l shut off the truck. It has lots of vacuum, I replaced the steering wheel buttons, still nothing. I noticed yesterday if l push down on the brake, the cruise light will come on and stay on till l release the brake. Like something is reading backwards.Seems very odd. I have a Lamp Out that comes on the truck also. All lights work, Have changed taillight circuit boards and bulbs ,tried  to change the brake switch but new one would not let me put it into gear. Will try another one as you can only set them up one time. I don’t know what else to try. PLEASE HELP. Thanks