I came home from working the night shift this morning to a house that was freezing cold. Checking our digital thermostat I noted it was only 12C. The thermostat was set for 18C. The heat sign was flashing which it does when the furnace is on, only the furnace was not on! I did the usual, checked the pilot light and the filter. Turned the furnace on and off using the thermostat. Reset the thermostat. I even banged on the side of the furnace. Nothing made a difference so I called a repairman.
Luckily the repairman was here within the hour. He checked the furnace and found nothing wrong with it. He finally determined that our digital thermostat needed new batteries! Although it appeared to be working normally, the display was lit and it was displaying the temperature settings etc. the batteries were so low they did not initiate turning the furnace on. So I ended up having a $113 service call to replace my thermostat batteries! From now on I will be changing my thermostat batteries every year when I change my smoke detector batteries.
Check those batteries everyone!