Testing Washer Control Board - Maytag MFR Series Service Manual

Disconnect power before servicing.
Replace all parts and panels before operating.
Failure to do so can result in death or electrical shock.

TeSTinG WaSHeR COnTROl BOaRD

Of All the parts that are returned to Whirlpool
Corporation for testing, that have been found
to have No Apparent Defect (NAD), it is by far
the electronic control that heads the list. More
control boards have been replaced in the field
without actually fixing the problem than any
other part.
There is not much to test on a control board
that is not basically visual, but depending on
the symptom or failure mode there are items
to test. Always check that all connectors
are firmly connected to the control board.
Sometimes, just unplugging a connector and
re-plugging it onto the control will correct a
problem.
If the failure displayed is a "Memory Failure" it
could be due to a small area failure in a fixed
Random Access Memory (RAM) chip that may
not cause this problem again for years. If a
Memory Failure occurs more than a couple
times a year, then it is cause to replace the
control board.
Blank displays can be checked by opening the
top of the washer and looking at the back side
of the control board. There is an LED that will
be lit if the control has power to it, this led is
located just above the transformer at the top
left side of the control when facing it from the
front of the washer; if this LED is not lit, then
the problem is probably not a failed control
board but a power issue.
Electrical Shock Hazard
First, look at the power supply connector to
see if it is connected properly on the control
board. Then check for proper power at the
connector, if these two items check out OK,
then look at the fuse on the control board. If all
three items check OK, then the control board
is defective.
If the "PWR On" LED behind the control board
is lit and the display is blank, make sure a
programmed EPROM chip is properly installed
in its socket, if so: it could be due to corrosion
at the contacts from the main control board
that go into the socket of the display board. It
is possible to disconnect the power connector
to the display. Loosen and remove the four
5mm hex nuts mounting the display onto the
control board. Pull the display off the control
board. This action will self-clean the terminals
and when the display is plugged back onto the
control board the corrosion could be cleared
away resulting in an operating display.
nOTe: When replacing a failed control board
that is out of warranty it could be a good idea
to remove, safely wrap and store the display
as a service part for future needs. Many
complete control boards are replaced yearly
that really only required a working display
board.
7-14