I have a total of 4 of these units which we use to control the temperature in the chick box. Controllers work fine until they stop. Of my 4, 2 have been rejected in the last few weeks. It looks like the errors are due to poor quality relays. If the unit switches to cooling after the limit has been reached, the heating relay will remain stuck and will not turn off the heating system, but will simply continue to heat while the cooling system light is on. This leads to overheating, which in our case leads to the death of the chickens. If you touch the device from the side, the relay will energize and everything will return to normal operation. I do not recommend this product!