No Filament Sensor with 4 pins?
The motherboard has 4 pin connector but Creality recommends a 3 pin connector addon.
Something wrong?
Hi @canuqc, welcome to the forums!
I believe none of the filament sensors have 4 pins on them, they are all 3 pin. One of the pins on the motherboard is not used and this is completely normal.
The product page of the Ender 3 V3 SE also shows in the optional accessories section a picture of the optional filament sensor which has 3 pins. So you should be safe to purchase the filament sensor on their website for the printer 
Ah, yes, thank u, what pins should I use?
Found it, support says only 3 pins used but they don’t say which.
You’re welcome. Don’t worry about which pins are used and which ones aren’t, the cable plugs are keyed so they can only be inserted into the sockets one way so you will not have to worry about wiring/pins as the filament sensor cable should be designed to just plug straight in to the mainboard and filament runout sensor
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Hi,
I have just bought the filament sensor for the Ender 3 V3 SE and have the opposite problem, the motherboard has 3 pins as shown in the instructions and the cable has 4 pins so will not fit.
Chers Rob
The problem has been solved by Creality support.
The instruction sheet with the filament sensor is incorrect.
Here are the correct instructions: Ender-3 V3 SE Filament Detector Kit unable to install | Creality Wiki