I get a call this afternoon. Seems some guy has purchased an R model tractor and it will not quit "buzzing" in the cab. The air needles indicate 120 psi and the truck moves back and forth with no problems. I say it is possible to have a defective air pressure sensor indicating a low air alarm if everything seems normal. He decides to drop it off at the shop so I can get a look at it. About 10 minutes later, the phone rings and the driver says it feels like the brakes are dragging but it runs good. I ask if he noticed any strange "smells" from the truck and he says no, but his wife following behind says the tires are "smoking". Thinking he is driving this thing with the brakes either adjusted too tightly, or the spring brakes not releasing, I drive over there. Sure enough the area around this tractor smells very much like burnt brake linings. I climb up into the cab and look at the dashboard. All three actuator knobs for parking brakes, trailer air supply, and tractor only brakes are black, not yellow, red, and blue as customary. To top this off, none of the locations/functions of the push buttons are in the normal place. The tractor brake only valve is on the far left as opposed to the far right, the parking brake release valve is on the far right, and the trailer, or emergency supply is in the middle. What ultimately was happening is that he got the trailer emergency valve depressed, and the tractor brakes only depressed which actually did nothing as it has no air supplied to it until the service, or parking brake valve is depressed. The long and short is he drove the the tractor seven miles with the spring brakes applied. No wonder it was smoking. After getting this figgered out alongside the road, he drove to the shop without further fanfare. I am now hired to straighten the "rats nest" out and put it back correctly, install the correct color knobs for function, and ensure it works as the truck was built to do. I don't know how it got this way and the truck was purchased out of state recently being delivered by freight hauler, (all I know). Rob