An appliance three blocks from the Atlantic is not the same appliance as one in
Baymeadows. It ages on exposure rather than on use, so the calendar predicts what
needs attention better than the cooking does — and the parts that go first are the
ones whose whole job is to move outside air or reject heat into it.
The diagnostic runs in an order for a reason: supply and grounding first, then
connections, then the airflow or gas path, and only then the expensive part. Roughly
sixty-eight thunderstorm days a year leave controls intermittent rather than dead, and
a board fitted into a supply problem is the same repair bought twice.
So the job is not just to replace what failed. It is to find out what the house is
doing to the machine, tell you plainly, and put the thing back into service in a
condition that survives the next season.