I installed a new, programmable thermostat today. I was very careful to make sure to wire it correctly, based on the wiring of the (very) old one. However, now the heat stays on indefinitely, regardless of the temperature reading (it was set at 70, but was reading out over 90 when I gave up and turned it off manually). Any thoughts on what I might have done wrong or where to start to figure it out?? At this point, it's going to be either very hot or very cold by morning!