siliconchip.com.au Australia’s electronics magazine May 2019 63
dishwasher. These traditional jets in
my dishwasher clean those upper trays
just fine; it is just the Waterwall sys-
tem that is failing to clean the bottom
tray properly.
From my research, I discovered that
if I’d gone down the more well-trodden
route of having a technician come out,
he would likely have gone through the
Samsung-recommended protocols of
swapping out a couple of pump mo-
tors, a stepper motor and gearbox, a
sensor array and finally the main PCB,
all at our considerable cost.
This unsuccessful repair scenario
was a much-repeated story posted
in the various forums, and I have no
doubt this would have been the case
with us too. None of these ‘fixes’ would
have resolved our problem.Finally figuring it out
From the video, I learned that the
noises I heard on cycle start were the
front vane moving along its usual trav-
el path to check nothing was impeding
it before the wash cycle started.
Indeed, one of Samsung’s helpful
suggestions in their troubleshoot-
ing guide is to ensure that nothing is
protruding through the bottom of the
lower rack, as this can stop the vane
moving and cause possible damage.
The front vane on my dishwasher
was moving OK; it just didn’t know
when it hit the other end, so the poor
old motor kept spinning and the gears
kept slipping, causing the noise. The
vane eventually gives up trying to move
and just stops where it sits, explaining
the noise and the lack of cleaning.
So, what tells the vane to stop when
it gets to the end of its travel? Simple:
a magnet mounted on the vane hits a
sensor mounted beneath the floor of
the chamber, and this tells the motor
to reverse and send the vane back to
the start position. I proved this wasn’t
happening by opening and closing
the door just after and during the
start cycle, to check on the progress
of the vane.
Sure enough, it hit the end and the
motor kept on going if I shut the door
again. Obviously, this wasn’t doing
the motor or gearbox any good, so a
fix had to be implemented before we
could continue using the dishwasher.
All the sharp troubleshooters out
there will have already deduced
that there are two possible caus-
es of this fault, the magnet and
the sensor.and these spin beneath the dish racks
and the blasting, hot and soapy water
cleans then rinses the dishes.
There are usually two of these rotat-
ing arms, one for the bottom rack and
one for the top. It is a simple system,
and while there is obviously other
stuff going on (water heating, pump-
ing, soap tray opening and drying cy-
cles), that isn’t relevant here.
In the Waterwall system, there are
two horizontally-mounted ‘vanes’ sit-
ting at opposite ends and spanning the
bottom of the washing chamber; one
is fixed at the far end, while the front
one is mobile and driven backwards
and forwards by a stepper motor.
The front vane is clipped to and
travels along a polished metal beam
running down the middle of the cham-
ber floor, and has a sharp curve on the
edge, facing the rear vane. The fixed
back vane has a series of high-pressure
water outlets equally-spaced along its
length, pointing parallel to the floor
and aiming at the front vane’s curved
surface.
The idea is that water is blasted
from the rear vane into the front vane,
which creates the titular “water wall”
as that vane traverses the chamber and
this is what mainly cleans the bottom
rack of dishes. There is now a video
on YouTube showing this operation
using three different cameras mount-
ed in the dishwasher, which explains
the process better than I can.
There are two other racks in the
dishwasher; one middle rack for cups
and glasses and a cutlery tray at the
very top, each with their own standard
rotating water jet
just like you’d
see on any other
Fortunately, by this time I’d found
the service manual and could test the
sensor (and many other parts for the
system) by using codes from the book
to run the different components indi-
vidually, without having to waste a lot
of time waiting for a cycle to complete.
Having this information was well
worth the hassle of finding the ser-
vice manual.
By holding down certain buttons
and pressing others, I could initiate
the vane travel test, and by placing a
magnet near where the vane’s magnet
would sit, I could stop it from moving
any further. This proved the sensor
was working, and that the magnet is
the problem; however, I already knew
this because of the YouTube video.
The guy in that video explained
that the plastic-coated iron magnet at-
tached to the vane gradually loses its
strength due to the constant heating
and cooling cycles.
His fix was to replace the magnet
with a much stronger rare-earth or
neodymium type. He simply took out
the old magnet, which is mounted in a
removable plastic housing, and glued
a whopping great rare earth one in its
place. His dishwasher then cycled
perfectly, and he sat back and basked
in the adoration of a grateful public.In the end, a simple repair
I didn’t have a rare-earth magnet of
that size in stock, so I tried various so-
lutions, such as removing some from an
old hard drive and cutting them down
to suit, but wasn’t overly successful.
I discovered that cutting these mag-
nets with anything severely diminish-
es their strength. Putting two smaller
neodymium magnets together side by
side also didn’t work well, so I went
looking for alternatives.
Jaycar has some in various sizes, but
those few with magnetic strength men-
tioned were only rated at most N35,
which is probably not strong enough.
I hit my usual go-to hardware-stores’
websites and found that both places I
frequent had various magnets listed at
a reasonable cost.
I ended up with a packaged pair of
N42-rated ‘door’ magnets, just the right
size at 25 x 7mm and for the princely
sum of just $25. I figured I could use
one and have a spare for when the
problem inevitably returns.
Unlike the guy in the video, I kept
the original magnet holder and sim-
ply shaped it a little to accommodate