HiLetgo 2pcs W1209 with Case 12V DC Digital Temperature Controller Board Micro Digital Thermostat -50-110°C Electronic Temperature Temp Control Module Switch with 10A One-Channel Relay and Waterproof

While there are plenty of professional fixes for central AC that freezes up, sometimes it's just a combination bad duct airflow, low outside temp, and/or too low thermostat set. Obviously you should make sure you aren't low on refrigerant or the air filter is dirty, but if you have old ducting or a miss-sized unit, it just happens sometimes (especially fall and spring). If your wallet doesn't mind the thousands of dollars to get a new AC installed or otherwise remedied, skip this. For the rest of us, this little gem you just provide it 12V (find an old wall wart, or buy one for a few bucks), cut one of the signal wires from the furnace to the AC (usually 2 of them, carrying low voltage AC, doesn't matter which one you cut), strip the ends on both sides of the cut and put them into the two relay legs (K0 K1), and then tape the temp probe to the copper coolant-in line. Set the setpoint to somewhere a little above freezing (5C or so), set P0 to "C" for cooling, and then set P5 (restart time) to 5 minutes. Now, if the line approaches freezing, it will cut out the AC unit outside while the furnace/air-handler fan still blows air over the too-cold coils warming them up. The restart delay prevents short-cycling the AC. Cheap, easy, works. Will mask a dirty air filter, but you're changing that on a regular schedule, right?

I used this as a fan controller for my motorcycle. I put the sensor into the radiator fins and dialed in the temperature I wanted to see on the temp gauge. The fan comes on and goes off precisely and crisply compared to the thermo switch that was impossible to find for an older bike. It now starts the fan smartly as opposed to groaning to life with the thermo switch. Just connect the device (+) source power to the running light circuit which comes on when the engine is running. For the fan, provide frame ground, and positive from battery, then through 10A fuse, then through switched relay onboard the device to the fan positive. The programming is simple if you google the device specs on YouTube.

These controllers work well and you can't beat the price. I'm using one to control a 20W silicone heater for an enclosed butter warmer. I keep the house cool in winter, and I got tired of mangling my toast when trying to spread cold butter. These don't have a parameter to switch from Centigrade to Fahrenheit display units like others do, but no big deal.

I only got one in the package. Was supposed to come with two. And waterproof lol. It should come with a tube of silicone if you’re gonna try to say it’s waterproof cause that what you’ll need to use. I’ve used these before and they work good is the only reason I didn’t send it back.

When it gets to 0 degrees, it shows HHH or LLL and shuts on and off, over and over again. This is bad for a compressor that is trying to control a FREEZER or refrigerator.