Slam Dunk Diagnostics with MST’s Ten-Step Troubleshooting Tango

By Scott Brown, Master Samurai Tech

Troubleshooting electric circuits is the single most common skill missing from 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 (MST), the online service training academy, developed the MST Ten Step Tango troubleshooting procedure, or TST. The TST is a coherent troubleshooting process, which I share below.

Many of the following steps should be done before arriving at the job so you can really 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: a) What is the appliance doing that it should not be doing? and b) What is it not doing that it should be doing? This step may seem 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. Familiarize yourself with it to see what you’ll be dealing with and then start wargaming. We call this “pre-diagnosis.”

3. Identify your LOI (Load of Interest)
Most of our troubleshooting problems in appliance repair come down to loads and switches. This is true even for computer-controlled appliances because the board is often 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.

5. Formulate a Troubleshooting Hypothesis
A hypothesis is just a fancy word that means “your best-educated guess.” This is not a wild guess; it’s based on all the work you’ve already done analyzing the schematic, plus your underlying knowledge of electricity and the technology used in appliances.

6. Identify Electrical Measurements
A hypothesis needs to be tested, and here’s 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
More schematic analysis — 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. The rule is: Do minimal disassembly for troubleshooting and save tear down for replacing the failed load or switch.

8. Perform Measurements
Only now do we actually start tearing things down! Only disassemble the machine as much as you need to, 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 specs in the tech sheet or service manual tell you what 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 disproven? 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 through the steps more deliberately to make sure you navigate the situation successfully.

Scott Brown is the co-founder of Master Samurai Tech (MST), a New Hampshire-based online training academy for appliance repair personnel, and a BrandSource service partner.