I come home tonight and the furnace isn't working. I troubleshoot: you know, make sure the switches are on, water level in the boiler isn’t too low, etc. Everything seems ok, but it appears that there is no power going to the electric low water cutoff. So I call the oil company and tell them what I did.
On the phone, he has me put a multimeter on the leads of the high-pressure controller, one at a time. I tell him the readings, and he tells me, "you see that curly pipe coming out of the bottom of it? Hit it with your hand as hard as you can." Furnace turns on. He says "I'll be by in the morning to blow out the gunk."
Why didn't I learn a trade? If I had a time machine, I would go back and give 20 year old Ian a slap and tell him to become a plumber.