I have a Maple Chase Item # 09620 thermostat. Last night, I replaced the batteries because the panel was displaying the 'lo bat' display. After replacing the batteries, the display still read 'lo bat' and the heat would not come on. I checked the cover to find out what further steps to take (I've replaced the batteries before and this hasn't happened). It says to replace the fuse if it has opened, but our fuse hasn't opened. Any ideas as to what may be wrong? Should we just replace the fuse anyway?