Panel Lights

Tonight we went for our monthly trip to Burger Burn at KMCW. We left in the dark and had a layer of broken at 3000 so turned on the Pitot Heat at takeoff. I decided to stay under the cloud layer as the winds were more favorable (still gusting to 30kts). When I went to turn off the pitot heat the panel lights immediately went out. They came back on in about 10 seconds. Like an idiot I turned cycled the pitot switch again and out went the lights. In ten seconds they came back on but only when the rheostat switch is turned up just about all the way. The lights are on high or not at all if I turn down the switch just a little. Cycling the pitot switch no longer affects the lights making them go away. Any thoughts? Does anyone have a schematic of the panel control system?