Garnet 709-RVC NLP Manual page 28

What to do in dual console systems if the two displays do not
read the same:
1. For dual display console applications, if the consoles disagree
the most likely reason is a bad console ground. Both console
grounds, and the sender grounds, must be connected
together with ground wiring. Do not depend on metal chassis
components. See item 2 in the following section for further
details.
What to do if readings jump or are inaccurate
1. We have had a few instances where 120VAC interference has
caused the readings to stall and create a gap; readings would
skip from 50% to 70% and then begin to function again. The
cause was wiring between consoles and senders being tied
too close to entrance boxes for shore power or bundled with
other high AC voltage lines or junction boxes.
2. Always ground the senders and the console to the same
ground circuit. This is very important; RV's can have several
ground circuits with resistance between them. We have had
instances where two consoles are installed with a different
ground for the service bay console and interior console. If you
see different levels from each console on the same tank, then
the ground circuit is not common. Connect both consoles
to the same ground back to the breaker panel ground point.
What to do if the system indicates a residual or non-zero water
level even though the tank is drained completely:
1. This can be due to a convex tank bottom or a sloped tank
bottom. In the case of the convex bottom tank a ring of water
may remain after draining. In the case of the sloped bottom
(to the drain valve side) a very small amount of water left in
the tank will result in a non-zero level indication. In both
of these cases, temporary installation of the sender using
duct tape or masking tape will allow the installer to check
the tank level before committing to a final sender position.
After cutting the sender to length and connecting the wires,
be sure to tape down both sides of the sender to eliminate
air gaps between the sender and tank surface which can
cause low signal strength and unpredictable performance.
The ends of the sender must be at least ¼" to ½" away from
the tank bottom and top to allow for wall thickness. The
exterior bottom & top of the tank are not the same as the
interior bottom & top; depending on the tank wall thickness
the inside height is ½" to 1" shorter than the outside height.
Knowing the wall thickness of your tank will allow you to find
the optimal sender position; placing the sender where it can
Page 28 709-RVC NLP Manual