Check the 12-volt DC power to see if it is connected to the battery and converter. If this connection is not made, the tank monitor will not operate. The lack of connection may cause power failure between the two. Also make sure there is a good chassis ground (the AC ground should connect to the chassis ground). If this is not connected it could be dangerous.
Check that the wires are not broken or the components are not loose. The wiring harness should be connected. Make sure the tank resistor harnesses are connected as well.
Check that the tank sensors and fresh water probes are attached and not rusted or damaged.
Replace any pieces that are damaged or attach necessary wires, using your owner's manual as a guide. Wiring will vary from model to model.
Clean the holding tank by draining out the water then wipe down with a mild cleanser. Tighten the tank connections, refill, and then check to see if the level reading is now accurate.
Check the voltage with an ohm meter if the tank lights are not coming on. Also check to see if the light bulbs are burned out. If so, replace the bulbs. If the tank lights are staying on, loosen the ground wiring and check that the wiring harness is tight.
