Dash & Running lights stay on with ignition key.

Hello friends and thanks in advance to anyone with a possible solution to my problem. It's a 2000 Peterbilt 379, Cummins N14 Celect Plus. The instrument panel & running lights come on come on when you switch the ignition key to the right or left position. It's a push button starter and engine will start when key is in either position. The weird part is that all the gauges come on and the truck will start and run, (with the push button) when you switch the headlights or running lights on with the ingnition key off. Instrument panel Iights being the lights in the round gauges and running lights being both amber lights on sides of headlights and taillights. The marker lights where the blinker lights are on sides of sleeper stay off, but do come on when you flip the marker light switch on. Dash lights will not dim with the adjustable dimmer either. I bought this truck just under three years ago and it's been this way ever since I've had it. It used to be a Freight Systems Inc. truck. I'm thinking they may have wired the lights in with the ignition for safety purposes, but that's just my opinion. I'm just tired of the lights staying on all the time and the fact that someone could steal my truck just by flipping on the head or marker light switch.