Level Probes - Bunn Axiom Series Service & Repair Manual

LEVEL PROBE SYSTEM
FIG. 17-1 LEVEL PROBES
Location:
The level probes are located inside the tank lid.
Operation:
The level probes sense the water level in the tank
by the conductive minerals in the water grounding
out the very low AC voltage applied to the probes. The
circuit monitors the time it takes the water to drop
the distance from the short probe to the long probe.
Proper "initial set up", and keeping mineral build up
off the probes/grommets, is required for this system
to operate properly. A brew abort feature is "built in".
In the event that the drop in water level from the short
probe to the long probe takes too long, the brew cycle
will abort and return to the main screen. This could
be caused by: Mineral build up on probes/grommets
(very hard water); probes shorting to top cover (verify
the mylar shield(s) are installed; plugged outlet (ie:
sprayhead limed up); incorrect operator use with the
pour over model (ie: pour in water and pressing "start"
button)
Test Procedures:
1. Enter programming level 2, scroll to "Refi ll". NOTE:
This screen only reads the long probe (blue wire) and
is used for setting the refi ll conductance threshold.
Alternate: Scroll to "Service Tools".
Then scroll to "LP1 & LP2". LP1 = short probe, LP2
= long probe.
2. A high reading (approximately 255) indicates water
is not touching, or not conductive enough to ground
the circuit. A low reading (0-2) indicates the probe is
grounded.
Removal and Replacement:
1. Disconnect the brewer from the power source and
allow tank to cool.
2. Remove nut, wire, and washers from probe.
3. Pull probe straight up from grommet.
4. When reinstalling, ensure long probe is connected
to the blue wire, and short probe is connected to the
brown wire.
NOTE: Heavy mineral build up on probes could indicate
that the tank, lid, and grommets may need to be de
limed as well.
Page 17
FIG. 17-2 LEVEL PROBES
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