Back to Basics – Fault Isolation with an Electronic Control, Part II

By Dave Bird, Instructor, Dyer Appliance Academy

Service/Diagnostic Mode is another electronic control feature designed to assist the technician with fault isolation and repair. The process for accessing the service/diagnostic mode is again a series of button pushes and knob turning that is different for each type of machine.

Once in this mode, the technician is provided with a series of choices that permits the testing of specific functions in the appliance. Sometimes an appliance can perform a series of functions sequentially or the technician can select certain individual functions exclusively. For example, in a front load washer you could open and close the water inlet valves, lock and unlock the door, turn the inner-tub to the left or right, perform a high speed spin or turn on the drain pump. Some machines permit the technician to review older fault codes that are not available unless you are in the service mode.

If any of the tests in the diagnostic mode fail, directions are normally provided to a specific testing section for that specific malfunction. These tests provide expected voltages or resistances that should be seen at certain test points at either the connector pins or component terminals. These troubleshooting tests are logical, comprehensive and systematic steps designed to determine and verify component failure.

With all that said, the question that I’m most often asked is “where can I find the tech data?” If you are lucky, there is a tech data sheet located somewhere in the appliance. If not, then you’ll have to get more creative and the answer is probably on-line. The UASA website has an excellent technical manual library for members ( that I’ve personally used many times when working in the field. Some manufacturer’s websites provide tech data, some do not. Some have it available for their machines but you have to pay a subscription fee to access it.

The trick is to find who has the data that you’ll use the most and then determine which is the most cost effective for your needs. And remember to be careful where you get your information from. Unless it’s from an official or reliable source, then you can’t always trust everything you find on the World-Wide-Web.

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