I have a temp. sensor (non victron) with 3 pins: red, black, yellow.
How do I wire it to certo GX ? There are only 2 sockets in the connector.
You can not just plug random temperature sensors into the Cerbo, there are many different types. Either buy the correct Victron one, or if you are competent at DIY electronics, the Cerbo sensor is based on an LM335Z. See the old comunity topic below.
https://communityarchive.victronenergy.com/questions/211871/temperature-sensor-diy.html