Troubleshooting and fault diagnosis
But first: what to avoid?
- Don't leap to easy conclusions! Have you taken into account all that you know about the problem?
- Avoid "blind alleys". If your current theory is not working, be prepared to admit that it might be wrong!
The first priority is learning as much as you can about the device you have in front of you. What category of product is it, what brand, model, and type? The product category is often obvious, but the brand and type might be more difficult to find.
You can find a lot of information on the label or prints on the device, like the label in the picture shown here which is a Steam Iron, Type GC7520, made by Philips. It works on 22-240V and consumes in between 2000 to 2400 Watt.
Check the manual or search the internet for information about the device, common failures, and informative teardown videos, e.g. “Philips AND GC7520 AND failure”.
There are lots of ways to gather evidence about the malfunction or failure:
- Description of the problem made by the owner/user (sometimes this can be misleading and/or 'wrong'). Check out the next section about “asking the right questions” to make sure you get the full story.
- Visual evidence and using the other senses. Further on in this article, you will learn more about the "SSST method", among other things. SSST will tell you how to use Sight, Sound, Smell, and Touch to pinpoint the failure mode.
- Describing the situation in which the issue started (what was the device doing, how was it being used…when the problem occurred, and what were the initial symptoms).
- Passive testing (e.g. with a meter - a resistance meter can be useful)
- Functional testing (when safe and possible).
Ask the right questions
Before opening up the device, it is important to understand as much as you can about the device/component and the circumstances under which it failed. You can do this by interviewing the owner (if it’s not you) and asking questions about the device. What symptoms did you or the owner of the device notice before and after the malfunction or failure? Was anything different compared to normal?
- Ask questions concerning the specific facts about the device like its age, usage history or past repairs.
- Ask about the operating conditions: how often has it been used in the past year (e.g never, regularly, on a weekly basis), how and where is it stored or used (e.g. in the cellar, garden shed or the attic) and by whom (e.g. yourself, kids or someone who borrowed it)?
- The third type of questions should be about the circumstances in which the device failed or started malfunctioning (e.g. did it fall into water, or on the ground? Did smoke come out of it? etc.).
- Finally, ask more specific questions about the order of steps taken before the problem occured. This gives you information on whether the device was operated in the right way, or not.
Try to be as specific as possible by asking the right questions: who, what, where, why and how? Don’t jump to conclusions too fast before finishing the interview. You can learn more interview techniques for asking the right questions in Skillful Questioning, Part 1 and Skillful Questioning, Part 2, which is part of the marvelous blog and book written by Jason Maxham: “The art of troubleshooting”.
Learn more on how your device works
When repairing something, it really helps to know how it works! This may sound obvious, but it's worth reading about how products function. You can find more information about how products work on YouTube, e.g. on a steam iron by using the following search terms: “site:youtube.com "steam iron" AND teardown”.
Check our article on how to search for repair info to get even more tips.
Identifying and locating symptoms
Once you’ve learnt more about the broken device, it’s time to identify symptoms and where the problem lies (cfr. the Fault detection and Location phase as illustrated in the figure below).
Once these have been identified, you can focus on that single section of the product (the Isolation phase) and start testing the components around it to check whether the isolated part is indeed the source of the fault.
With all this information, you should be able to assess the possible solution to the problem. For example, changing a component, cleaning or lubricating the product, or glueing a part back together, in order to complete the repair.
In the rest of this article, we focus on the Fault Detection and Location phases, helping you to identify and list the symptoms and give you ideas to locate the source of the problem. After this you need to decide whether to carry out the repair yourself, to visit a Repair Café, or to bring your product or device to a professional repair shop.
Sight, Sound, Smell, and Touch
Some of the problems with your product may be easy to detect by using your senses: Sight, Sound, Smell and Touch (SSST).
When identifying and locating symptoms, start by trying to operate the product and observe its behaviour or response. In some cases, you’ll need to disassemble your product partially in order to identify failures in internal components. In that case, ALWAYS unplug your product before disassembling it.
In general, the product will probably do one of the following:
- Product doesn’t respond: for example, the product doesn’t turn on at all or is “stuck” on a specific position or function. First check if your device is powered: is it connected to a mains supply or power source? Or is the battery charged? If it is powered and still unresponsive, there is a big chance a fuse may have to be replaced or there’s another failure within the electrical system of your product (e.g. a broken switch).
- Product works intermittently: for example, the product starts working well but then suddenly stops. In this case a resettable fuse is often the problem. The fuse will shut down the device after a long period of high current draw and will reset itself after a short cooling period (e.g. for blenders and mixers).
- Product shows an error code or signal: look for these signals. They may be on the display of the product (if it has one), or it may be shown by blinking lights or alarm sounds. Consult the manual or search the internet to find out what the error code or signal means. Use the right terms to find your information fast, e.g. “Krups AND blinking light”
- Product underperforms: the main function of the device is below-average, e.g. when the coffee comes out too watery, or the vacuum cleaner doesn’t seem to have the same suction power.
When power, fuses and error-code solutions can’t help you fix the fault, you need to do further inspection of the device using the SSST method. We'll guide you further into this methodology in an in-depth article.
Become a professional troubleshooter
Troubleshooting is learned by doing. The more you try things out, look things up, talk to fellow troubleshooters, and—most importantly—talk to the owners of broken products, the easier you will get to the root-cause of the problem.
There are many books about electronics repair, but they mostly focus on analog troubleshooting techniques. When you want to know more about general approaches to troubleshooting and find the failure mode, the blog and book of Jason Maxham is a must and fun read: “The Art of Troubleshooting”. A list of troubleshooting strategies can be found here: Strategies.
Source of this information
The information shared in this article is based on research on problem diagnosis executed by TU Delft. For the original sources of information, please check:
Restarters (2021). For the original article, please check Diagnosing faults - Restarters Wiki
Davidson, H.L., (1999).“Consumer Electronics Troubleshooting and Repairing Handbook. The three S’s, p.5.
Pozo Arcos, B., Bakker, C., Flipsen, B., & Balkenende, R. (2020). Practices of fault diagnosis in household appliances: Insights for design. Journal of Cleaner Production, 265, 121812. https://doi.org/10.1016/j.jclepro.2020.121812, Researchgate: Practices of fault diagnosis
Maxham, Jason (2011), The art of troubleshooting, book and website: THE ART OF TROUBLESHOOTING