A couple of weeks ago my evaporative air cooler (known colloquially as a "swamp cooler") appeared to be on the fritz. Air was blowing through it, but it wasn't cool air. A few days prior, I had reinstalled the copper tubing that supplies the water to the unit, oiled it, and it had appeared to be working. Now, after a long day at work, it was still over 90 degrees in the house as it began to get dark. I got out the ladder to take a look. I had not turned off the unit, so the belts and pulleys were moving inside of it. I really didn't want to stick any parts of my body inside to figure out what was wrong, but I spotted it right a way. The hose that supplies water from the pump to the pads had come unhooked from the pump. I saw the end of the hose, that should be attached, and a connector to which I connected it and it was great--done in five minutes.
Until the next time it got hot enough to use a couple of days later. It still wasn't cooling. I was thinking that the pump must be bad, and that instead of spending the night peacefully at home watching a movie or playing a game, I'd be heading to Home Depot for a new pump and installing it. Once again, I climbed up to take a look, this time with it turned off.
At once I began to laugh at myself. I had hooked the loose end of the hose not to the pump, where it needed to be hooked, but to the drain spout. The pump was working all right, but it was sucking in water then spitting it right back out into the pooled water in the bottom of the swamp cooler. I quickly made the appropriate reconnection and the thing ran like a champ.
I think the ability to laugh at oneself is healthy, but if you can't laugh at yourself, go ahead and laugh at me.