Companion to the lesson "Diagnose It Right the First Time." One sheet per job; file it as your private pattern database.
Job header
Date: Customer: Appliance / brand:
Model number: Serial: Model/serial photo taken: ☐
The model number gets you the wiring diagram, the parts list, the service bulletins, and the exact replacement part. Photograph it before you open anything.
Step one: symptom interview
"Walk me through what happened. What was it doing before it stopped? Did anything change, a noise, a smell, a power outage? Has anyone worked on it recently? How old is it?"
Symptom as described:
"Dryer runs but doesn't heat" and "dryer died completely mid-cycle" point at different components. Write the answers down; a symptom described accurately is worth an hour of testing.
Step two: identify and reproduce
☐ Machine identified, model/serial photographed.
☐ Fault reproduced and observed myself. Document what the machine does and does not do:
☐ Error code noted (testimony, not verdict: the code narrows the search, the meter decides).
Step three: inspect, then test in order
☐ Machine unplugged; non-contact voltage tester confirms power off.
☐ Wiring diagram pulled (inside the machine or a parts site).
☐ Components tested in circuit order (multimeter: continuity and resistance; amp clamp: current draw).
☐ Second reading taken before quoting (leads slip; misread resistance sends techs to the parts counter for parts that were fine).
☐ If readings disagree with symptom: subsystem isolated on the bench / compared against a known-good component.
Step four: test before order
Suspected component
Test performed
Reading
Condemned?
☐
☐
Never order a part you have not proven bad. Electrical parts and control boards are largely non-returnable once installed; the classic beginner loss is a $140 board, wrong diagnosis, dead inventory, and a second parts charge on the same job.
Step five: fix, verify, document
☐ Repair run through a full cycle (reach temperature, spin, drain, ignite), not a thirty-second victory lap.