Diagnosing and repairing control board failures is difficult and complicated. The tech sheet that I see for this model indicates that the CCU (Central Control Unit or main control board part 8183251) should be replaced if the drum is not rotating and the user interface if it is. The second image below shows this technical information for the F70 code. There are 2 user interface control boards in this washer. In addition to part 8183271, the center user interface part W10168595 could also cause this problem. I am aware of advanced diagnostic checks that can be made to determine the cause of the problem that go beyond the information that is provided on the tech sheet. These checks could prevent replacing unnecessary parts. Here are the advanced checks that the technician would need to complete that would accurately diagnose the cause of this failure:
Unplug the washer for 5 seconds. Plug it back in and wait 30 seconds. This is to reset the control.
Disconnect the MI3 connector (The MI3 connector is a DCV connection for communication between the Motor Controller and the Machine Control Board.) at the control board. If the display lights up either you have a shorted harness or a shorted Motor Controller dragging the DCV down.
Reconnect the MI3 connector to the Machine Control Board, and then disconnect the MI3 connector at the Motor Controller. If it lights up you have a shorted Motor Controller and need to replace. If it does not light then the wiring harness is shorted.
If it still does not light and you have 120VAC to the control. Start disconnecting the loads from the Machine Control one-by-one, like the Thermistor, Flow meter, Pressure Switch etcâ€¦ until it lights up if so check that component and wiring to the component. "
If it still will not light up check the DCV out of the Machine Control to the User Interface to make it light it up. NOTE: THE VOLTAGE CHECKS ARE NEGATIVE DCV. PIN #2 IS THE REFERENCE POINT FOR THE CHECKS.
Unplug the harness to UI and check with a DVM or VOM on (Connector UIP3) if correct voltage is present. Pin 1: -5V, Pin 2: 0V, AND Pin 3: -12V. (-12VDC is for the Buzzer only, the -5VDC check is for the display).
If the DCV voltage is not present and the CCU has power at (IF2.1 to IF2.2) then the CCU is broken and will need to be replaced
If the DCV is present disassemble the UI and check the Interconnecting cable on the UI that goes from the Center UI to the Right UI for a loose connection. Disconnect and inspect the connectors on the harness for being bent, as well as look at the control pins to make sure there is not a build up of varnish coating the pins. If so gently scratch through the coating and reconnect the connectors to both user interfaces.
If no connections issues are found remove the interconnecting cable that goes from the Right hand interface to the Left hand interface from the UI (connector J004) and check for 4 to 5 VDC on the board at the white and black wire on the pin connector J004. NOTE: IF YOU DO NOT USE NEEDLE PROBES YOU WILL HAVE AN ALMOST IMPOSSIBLE TIME GETTING THE PROBE TO GO INTO THE HOLE TO MAKE CONTACT WITH THE BOARD TO READ THE VDC. The first image below shows photos of the J004 connector and the check points.
These tips should help the technician to accurately determine the cause of the F70 code. Since the CCU was replaced it is unlikely that this is the cause of the current F70 code. These advanced checks should be performed by a technician with the proper equipment (volt/ohm with needle probes). If you need more help, resubmit your question with additional details.