[rainforestosc]

My thermostat is blank and the batteries are not the problem. How do I check and identify the cause of the limit trips?

[acetc]

You should check for power to the furnace or air handler, if you are sure you have power then you need to check the transformer and the fuse in the printed circuit board. You are not getting 24 volts to the thermostat if you are then you probably have a bad thermostat. Good luck < Mike