I can't say for sure but many circut boards or thermostat boards will have what is called a dip switch on the board it self. this is a small I mean tiny switch. Often you will have a set of them together so their easy to find. You will need a small awl or knife poilt to switch it as it is that small. It should be marked on the board so you can find it. Also on some if you simpley hold the temp button for fivr or ten seconds this will switch it for you but I think yours will have the dip switch. Good luck.