Mary Knize

Air conditioning float switches for dumb homeowners

2 min read


Last year, right after moving into our new house, our air conditioning started acting weird. The thermostat would randomly turn itself off in the middle of the day. In Florida, in late spring, it's no fun to randomly lose A/C.

Since the thermostat seemed to be broken, I opened it up to see that there were no batteries in it. Because I know nothing about thermostats or air conditioning units, I thought, "Gee, maybe I should put some batteries in this!" For some reason it never crossed my mind that it had been working fine without batteries for months.

But that fixed the immediate problem, and we had the A/C chugging along happily for a couple of days.


We started noticing a strange residue on the tile floor around the air conditioning unit. We also noticed that it looked a little wet. We took the vent cover off the wall and discovered that the duct was filled with water. Then, we opened up the little door to the air conditioning unit and saw that there was a bunch of water in there, too.

What happened? Well, it turns out that there was a float switch on our air conditioning unit that had killed the power to the thermostat when it reached a certain water level, and putting batteries in the thermostat circumvented that safety measure.

Photo of air conditioning float switch


We immediately bought a shop-vac to clean up all the water, and to also fix the problem. It turned out that the drain pipe for the air conditioning was clogged. A bunch of sludge and gunk came out of the drain pipe, and once the water drained out, the air conditioning began working again.

Jump forward a year and we're having the same problem again. Our air conditioning is intermittently turning off, and we're finding water in the drain line. This time, we've had to take the shop-vac to both the inside and outside ends of the drain pipe. We've also flushed the line with A/C drain line cleaner. We could've also used distilled vinegar, but the A/C line cleaner was relatively inexpensive, and had great reviews.

Some of the reviews on the drain line cleaner suggested using it every two or three months, so it looks like we're going to add this cleaner to our normal routine when we change the air and water filters.

Canonical URL