We woke up to a very cold house this morning and found our furnace was not running overnight. Of course it's the coldest night so far this year, go figure the luck.
I checked out the obvious - thermostat and main fuse and both were fine. The control board was flashing Code 24, Check for short circuit in secondary voltage 24VAC Wiring and after removing the service cover I found the 3 amp fuse was blown.
I do have electronics repair experience, have a multimeter and a good understanding of some of what I'm looking at on the board. Before I run out to grab a replacement fuse I thought I'd see if anyone had any other suggestions - relays to check or other components on the main board that might cause the fuse to blow.
Carefully follow the wiring above the burners and see if any of it touched the ventor fan to the chimney and got melted and shorted. Seen that happen several times. Look at all your tstat wiring where it enters the furnace for poor condition/shorts to ground.
Thanks for the reply, Yuri. I replaced the fuse, made sure there were no melted or shorted wires and got the furnace back up and running. So far, no problems. I guess a surge might have blown the fuse since we've had no problems for 2 years and none for a week so far. Thanks again for the advice.