Garnet SEELEVEL II 709-LL Manual page 23

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
"see" the water will ensure proper level calculation and sender
operation.
2. The signal strength should be in the 50 range for best
performance. If the signal strength is in the 20 range it is
indicative of a high resistance in a connector, a bad ground,
or improper bonding of the sender to the tank (a possible air
gap on one or both sides of the sender).
3. With the console installed you can check level on each tank, if
you get an indicated level of 10% to 20% and you know this is
too high, reposition the sensor board as follows:
a.
b. On sloped tanks, which are used to promote complete
4. The close proximity of metal to the sender can be misinterpreted
as water, since they have similar electrical characteristics. Any
709-LL Manual
In the case of a convex tank bottom, usually found on
large flat tanks, raising the sender is the best solution to
accomplish a zero reading when the tank is empty. This
may result in having to shorten the sender by an additional
segment.
draining, one alternative is to measure the end of the
tank opposite from the drain valve. It may be necessary
to extend the wire harness to be able to measure on the
optimal side. On the drain valve side, the best choice is to
elevate the sender to avoid reading a puddle at the drain
valve.
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