No heat

Found my 3a fuse on furnace board was shot. Replaced it. So far so good
Obviously, if it goes again, I will get service.
As far as what caused it to go bad, no idea. I didn't touch anything prior to noticing no heat. Thanks for your help.

Furnace has been running fine since replacing the fuse. Looed for bare wires. Couldn't see anything out of the ordinary. Could the fuse have just been week?

Fuse blew again. I don't see anything that is an obvious problem. While I was in the furnace room with the furnace running, I heard a loud clicking which appeared to come from my Honeywell humidifier solenoid. Based on my control board where the humidifier is wired to, the humidifier was energized and I could see that water was discharging from the bottom. Question: could the clicking solenoid be the problem?

Heat ran fine throughout the night. Had the tech out this morning since I couldn't find anything obvious. Checked everything indoors. Didn't find anything. HE found the problem within my outside unit. There was a wire laying barely rubbing one of the interior copper pipes. There was a minute area where the wire was bare from rubbing. Taped it up and moved the wire away.

Thank you for your replies.