Garnet 709-RVC NLP Manual page 30

for the wall thickness when positioning the sender board
(usually ½" to 1" margin from the outer shell). If the sender
is positioned above the vent then the maximum reading may
be less than 100%.
7. There may be a buildup on the inside walls of black and grey
tanks. We get calls occasionally about older coaches that have
not been in service for a few years in which the black tank will
now indicate a level even though it is empty. The likely cause
is that the tank has a significant build-up, probably exceeding
¼" to ½"thick! Redex is not an acceptable chemical to promote
clean tank walls; it is far too slow to get the breakdown action
started. Use an RV type of liquid chemical, we suggest Tissue
Digester, Sensor Cleaner, or the latest we have used called
Happy Campers Holding Tank Extreme Cleaner available at
www.happycampersworld.com.
trip, leave with a high concentration of the chemical in the
tank and approximately 30% full of fresh water. Hopefully
you can drive for 2-3 days allowing the tank levels to rise
through normal use. We recommend that you exceed the
level that you see the system report when the tank is empty.
After the sloshing and the soaking hopefully the build-up will
be flushed away when the tank is drained and flushed. If you
still have symptoms the treatment may required a few more
times. The waste did not build up on the tank wall in one day,
so it may not dissolve in one treatment! The build-up looks
like water to the system since it holds a significant volume of
water in the build-up area. It takes much more than a film or
piece of tissue to cause the error.
What to do if the system reads a zero water level at all times,
or does not reach 100%:
1. This may be due to excessive tank wall thickness. We have
tested the sender on an actual tank with
to ensure proper operation. If you encounter an excessively
thick tank wall the symptom will be a zero reading regardless
of the actual tank level. The cross check would be to test
the sender on another tank by taping it in place temporarily,
if it now works the tank wall thickness is well over
can also use a 1 gallon jug or a 5 gallon pail as a test tank to
crosscheck operation of the sender.
2. A symptom we have seen is the sender will not indicate 100%
when the tank is full. If the sender is positioned too high on
the tank, then water cannot reach high enough on the sender
for it to read 100%. The top of the sender must be at least
¼" to ½" away from the top of the tank to allow for wall
thickness.
Page 30
The next time you take a
3/8 " wall thickness
709-RVC NLP Manual
3/8 ". You