The first sending unit on my CK30hst was faulty. I pulled it out of the tank and put a meter on the fuel gauge wires. While moving the sending unit float manually through its travel, the readings bounced all over the place and not a steady increase or decrease (depending on going from full to empty or empty to full) within the specified range. I replaced it with a new one and found the float to bump the side of the tank and stick at times. A little bending to the wire float arm corrected the problem. I can get the min and max readings for you if needed but don't know if they would be the same for your model.