Troubleshooting electric circuits is the single most important and also commonly-missing skill among appliance techs today. It is also the single most profitable skill, even more than sealed system repair, because it is needed on many more service calls.
Most appliance techs are competent at making mechanical repairs. But when it comes to electrical problems, which comprise the more profitable repairs, most techs today do not know how to use the schematic to troubleshoot or even what troubleshooting really is.
Troubleshooting is not an art; it is a science with a logical flow of thinking. To bring this skill back into the appliance repair trade, Master Samurai Tech developed the MST Ten Step Tango (TST) troubleshooting procedure. The TST is a logical, coherent troubleshooting process that offers a systematic approach to identifying the correct problem the first time. No guess-work, no hail-Mary’s on replacing the control board and hoping to “get lucky.”
Here’s a brief description of each step. We teach this process in our Core Appliance Repair Course, and then implement it in many virtual case studies in some of our advanced courses as well as webinars.
Many of these steps should be done before arriving at the job, so that you can save time, minimize liability (from unnecessary disassembly) and impress your customer with your confidence and efficiency.
1. Formulate your problem statement
This means taking the often confusing and lengthy problem description that the customer gave you, picking through it for what’s actually relevant and useful, and crafting a short problem statement that will guide your next steps. A good problem statement will answer one or both of these questions: 1) what is the appliance doing that it SHOULD NOT be doing? and 2) what is it NOT doing that it SHOULD be doing? This step seems obvious, but many a tech has gone down time-wasting rabbit trails by not taking a moment to do this.
2. Schematic overview
Before you even look at the appliance, you should get out the schematic and familiarize yourself with it to see what you’ll be dealing with and start wargaming. We call this “pre-diagnosis.” Do not skip this step!
3. Identify your LOI (Load of Interest)
Most of our troubleshooting problems in appliance repair comes down to loads and switches. This is true even for computer-controlled appliances because often the board is functioning as a switch for a load. Troubleshooting always begins at loads, not switches. The LOI is not necessarily the part you think has failed. Rather, it’s “the thing that ain’t doing its thang.” Whether the load itself has failed or another component in its circuit is at fault is exactly what the rest of the TST will determine.
4. LOI circuit analysis
We still haven’t touched the appliance yet! First, we’re going to wargame our service call by identifying all the components that are in the LOI’s circuit — other loads in series, control boards, and especially any switches in the LOI’s power supply circuit. We’ll also note the various technologies we’ll be dealing with and any specifications that will be useful. Again, the more of these steps that you do BEFORE going on the job the better. You’ll be more relaxed and make fewer mistakes when you are not under the watchful eye of the customer while you look over the tech documentation.
5. Formulate troubleshooting hypothesis
Hypothesis is just a fancy word that means “your best educated guess” as to what is causing the failure with the LOI. This is not a wild guess — it’s based on all the work you’ve done already in analyzing the schematic, plus your underlying knowledge of electricity and the technology used in appliances. A good hypothesis will be short, specific, and lead directly to a test. Avoid saying vague things like a component is “bad.”
6. Identify electrical measurements
A hypothesis must be something that can be tested, and this step is where you figure out the best way to test it. For example, if your hypothesis is that the LOI is not getting its voltage supply, you would measure the supply voltage for that load.
7. Identify test points
Time to look at the schematic again — you want to find the most convenient points at which you can make your test. Most of the time, these measurements can be made right from the control board or timer, since that is almost always one of the easiest and most central components to access. We call these “EEPs” (Electrically Equivalent Points) and teach you how to find them in our courses. The rule is: do minimal disassembly for troubleshooting, save tear down for replacing the failed load or switch.
8. Perform measurements
Only now do we actually start tearing things down! Disassemble the machine only as much as you need to make your tests.
9. Compare measurements to specs
A reading on your meter doesn’t mean anything unless you know what you’re looking for. The specifications in the tech sheet or service manual tell you what reading to expect. Based on that, you can determine if your measurements prove or disprove your hypothesis.
Was your hypothesis proven? Proceed with Step 10. Was it disproved? No worries. Hop back to Step 5, make a new hypothesis, and proceed from there.
10. Make the repair
Once the fix is in, don’t forget the vital last step: check for proper operation! Don’t walk out of the customer’s home until you’ve shown that your repair actually did the trick.
Once you have gained experience, these ten steps will flow quickly from one to the next without really having to think about each one. Just like a dance! However, when faced with any kind of unfamiliar or tricky repair, you can slow down and go more deliberately through the steps to make sure you navigate the situation successfully.
You can learn all the basic electricity and technology skills you need to effectively apply Ten Step Tango with understanding and precision right from your computer with Master Samurai Tech’s on-demand, self-paced appliance tech training. Click below to check out the Core Appliance Repair Training Course right here at the Master Samurai Tech Academy.