Yes, if you replace the sensors you have to calibrate. Bad news is, you have to really have the Calibrate sheet that came in the owners pac of the Motorhome. It has the values for each tank to program. But, you can still calibrate without that sheet. You may have to measure the tanks and there is a chart for assigning the various inputs. This link will help. You may be able to calibrate by inputting the Empty and the FULL according to this link. Alladin has 2 systems. The FULL version and the Jr version. Doug
http://www.tckempke.com/HRNav/Aladdin-System-Users-Guide-05.pdf