My Ultimaker 2 Extended+ motherboard has 3 temperature sensor inputs: Temp 1, Temp 2, Temp 3. The Temp 3 is for the bed and the Temp 1 and 2 are for 2 potential extruders. Now my printer has only one extruder and I have no intention of adding another one any time soon. The Temp 3 input is for the bed and the connector got removed from the PCB. I tried soldering one but it didn't work (I failed miserably). There is no hope of ever using the temp 3 input again.
I was thinking of changing the firmware so it reads the temperature of the bed from temp 2 instead. I will upload the source code tomorrow.