As a first step, try to find the user manual supplied with the device.
If you can't find it, chances are you can find it on the internet. The first thing to do is to find the brand and model number of your device. This information is usually found on the product label, which is often attached to the bottom of the device. Here are some examples: AEG SB4400, Tefal BL439D, Domo DO710BL,...
Once you have this reference, try to search it in the database of this website.
If you can't find it on this platform, just try searching the following terms on Google: [brand] [model number] "user manual"
When you have your manual in front of you, go to step 2
Look in your user manual for information on how to interpret the light signals of your device. Also check whether there are any special procedures (cleaning, maintenance,...) that you have started in spite of yourself, which would explain the strange behaviour of the device.
Read all the 'warnings' items at the beginning of the user manual.
If you find a logical explanation for your device's signals, it may not actually be malfunctioning, but simply needing to complete a procedure by pressing a button or performing an operation described in the user manual.
General repair tips :
Caution
This tutorial was written by Repair Together - the network of Repair Cafés in Wallonia and Brussels (Belgium)
With this project, we try to create relevant guidelines on a product category and frequent faults level. The exercise is led by different repair networks, but our content can only grow and improve thanks to your help.