Maytag MFR Series Service Manual page 172

Communication errors are the most
common and hardest to diagnose. This
is one of the first things to check if there
is a communication error. Unplug the
communication wire while checking for
corrosion or damaged wires before plugging it
back in.
E500 inverter has POWER indicator to show
inverter has power supplied. D700 has a lit
display indicating power supplied.
E500
POWER
Indicator
There are two LEDs on the back of the control
board that show communication between
the control board and the inverter. The LEDs
are located a little right of the top center of
the control if facing the front of the washer.
The LEDs are marked RX for Receiving
communication and TX for Transmitting
communication.
Rx & Tx
LEDs
If both lights are not on when a cycle is started
then there is an issue with communication,
which can be caused by the wrong parameters
sent to the inverter, or a failed EPROM chip.
Parameters can be resent to the inverter
anytime there is not an active cycle running
and it does not take long to work through
this exercise whenever the control has
malfunctioned and prior to replacing a control
board or an inverter.
Before re-sending the parameters to an
inverter check that the control is programmed
to be for the correct washer by consulting the
Model Number Conversion Table
(See page 1-3).
A higher percentage of replaced inverters are
due to failed communications between the
inverter and the control board, than for any
other reason. Failed communication always
D700
displays failure code 27 on the control display,
Lit Display
or in a failure to load parameters during an
initialization process.
TeCH Tip: if there are more than a few
Maytag mulit-load washers that are being
maintained and / or serviced, Maytag
recommends that the technician keep a known
good communication cable from a larger
washer as a service tool, and / or emergency
replacement part. The communication cable
for the 80 pound washer will be long enough
to service any of the MFR line of washers.
Communication Cable Part #23004210.
Check and clean cooling fans associated
with the inverter. Most inverters have cooling
fans mounted to the cooling fins (heat sink)
of the inverter. Cooling fins clogged with lint
and dirt, and faulty cooling fans will result in
appreciably shorter inverter life.
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