8) checker still caries the old style glass fuses, and when you look at the heater controls, one is for heat(on or off), one is for the temp control(the amount of heat or cool air coming out of the vents), and one is for the defrost(on or off). to get heat push the heat and temp levers down all the way for max heat, and use the temp lever to control the heat. for defrost push all three down.