Review on 🌡️ HiLetgo Temperature Controller Thermostat: Advanced One Channel Test, Measure & Inspect Device by Logan Collier

You won't find an instruction manual but you will find this temperature relay/controller if you search the web for W1209. Most important: After connecting the 12V source and grounding, the relay terminals K0 and K1 open or close depending on whether the relay is active (red LED lit) or not which are switched on/off by the relay.It can be configured to that it turns on when the maximum temperature is reached (for cooling) or when the minimum temperature is reached.You can use two of these to alternatively control the heating of the cooling element as needed, i.e. to create a thermostat with a configurable temperature range. For example, you can connect this relay in series via terminals K0 and K1 with !2 V power supply for the fan to cool the battery cal temperature is reached In this case, the circuit opens and supplies power to the fan for optimal cooling of the batteries. (If your fan isn't working, you can set an alarm - setting P6 - that will go off at a critical temperature.) There are other features that can be configured using features P0 - P6 (google them for details).