Is your Shelly 2.5 humming? Making strange noises or constantly dropping the Wi-Fi connection? Then you are probably familiar with the frustrating problem that many Shelly owners face: after a few years, these devices become increasingly unreliable.
What looks like a Wi-Fi problem at first usually has a completely different cause. The good news: in most cases you can fix it yourself with a 50-cent repair!
Update September 2026 – my long-term experience: Every Shelly 2.5 I repaired this way eventually failed again with the same defect – even though I used a high-quality 105 °C capacitor. The repair reliably brings a dead device back to life, but it’s more of a stopgap than a permanent fix. Details and tips further down.
The Problem: When Shellys Get Old
Recognizing the Typical Symptoms
Shelly 2.5 devices of the first generation in particular show characteristic problems after a few years:
- Strange noises: Humming or buzzing from the device
- Unstable Wi-Fi connection: Sporadic disconnects
- Unreliable operation: Commands are not executed
- Complete failure: The device stops responding entirely
In the video I demonstrate the characteristic sound — if your Shelly sounds like that, there is a good chance this repair will help!
The Root Cause: Capacitor Aging
What many people do not know: the problem is usually not the ESP8266 chip or the antenna, but a tiny electrolytic capacitor in the power supply. After years of use, it loses its electrical properties and destabilizes the entire power circuit.
The tricky part: the capacitor looks completely normal from the outside — no bulging, no visible damage.
The 50-Cent Repair, Step by Step
What You Need
- 100µF/16V electrolytic capacitor (approx. 50 cents)
- Soldering iron and solder
- Narrow flat-head screwdriver
- Some patience and care
Important safety note: Never work on the Shelly while it is connected to mains power!
Opening the Case — the Flat-Head Screwdriver Trick
Opening the Shelly 2.5 is a little tricky, but perfectly doable with the right approach. In the video I show you exactly:
- Where to insert the flat-head screwdriver
- How to carefully pry off the casing
- What to watch out for with the delicate tabs
The trick is to work systematically along the sides without applying too much force.
Identifying the Faulty Capacitor
Once opened, you can see the compact circuit board with all its components. The problematic capacitor is the small black cylinder marked “100µF 16V”. In the video I explain exactly:
- Where the capacitor is located
- How to distinguish it from other components
- What other capacitors are present on the board
Removing the Faulty Capacitor
Desoldering requires some skill, but is very manageable with the right technique. I show you in the video:
- How to carefully tilt the capacitor out
- The correct soldering iron technique
- How to clear the holes after removal
Particularly important: the capacitor sits on the outer edge of the board and is therefore relatively easy to reach.
Installing the New Capacitor Correctly
With electrolytic capacitors, polarity is critical:
- Negative pole: Marked with a broad stripe on the casing
- Positive pole: The longer lead
In the video I show in detail how to correctly identify the polarity and orient the capacitor. Getting this wrong would destroy the entire device!
Reassembling the Case
When reassembling, make sure to route the Wi-Fi antenna correctly. There is a dedicated notch in the case for it — the video shows you exactly how this works.
The Success Test — Live in the Video
The most exciting moment: switching it on for the first time after the repair! In the video you can watch live:
- How the repaired Shelly boots up
- Testing the web interface
- Checking the relay function
- And most importantly: the listening test reveals complete silence!
After a successful repair, the Shelly runs reliably again – for how long, see my update.
Other Affected Shelly Models
The capacitor problem is not limited to the Shelly 2.5. Other models can be affected as well:
- Shelly Dimmer (first generation)
- Shelly 3EM (older versions)
- Other first-generation Shellys
The repair principle remains the same — only the exact capacitor type may vary.
Why the Repair Is Worth It
Sustainability over the Throwaway Mindset
Instead of discarding working hardware and buying new devices, you invest 15 minutes and 50 cents in materials. That is:
- Environmentally friendly: Less electronic waste
- Cost-saving: A new Shelly 2.5 costs over 20 euros
- Educational: You understand your hardware better
Long-Term Reliability
After the capacitor repair, the Shellys work like new again:
- Stable Wi-Fi connection
- No more strange noises
- Reliable response to commands
- More service life – though not permanently in my case (see update)
Practical Tips for the Future
Preventive Measures
Electrolytic capacitors age faster due to:
- Heat: Avoid excessively warm installation locations
- Moisture: Ensure a dry environment
- Overvoltage: Use surge protection
When Is a Repair Worth Attempting?
The repair is most promising for:
- Devices older than 2–3 years
- Typical noise problems
- Sporadic Wi-Fi dropouts
- Devices that are still partially functional
Update September 2026: How long does the repair last?
A year after this article, I have to be honest: every Shelly 2.5 I repaired eventually failed again with the same defect. That’s why I’ve done this repair more than ten times in total.
And I didn’t use a cheap capacitor, but a Panasonic FR, 100 µF/16 V, 105 °C, low ESR (Reichelt: FR-A 100U 16B).
What I know now:
- The Shelly 2.5 contains three electrolytic capacitors: the 100 µF/16 V one replaced here and two 4.7 µF/400 V – according to Hackaday, all from a budget brand. I only replaced the 100 µF capacitor. The community now recommends replacing all three with 105 °C brand-name parts no larger than the originals. Whether that makes the devices last for good, I can’t say.
- The root cause remains: the device is very compact, the power supply parts sit close together, and it gets warm inside a closed wall box. A new capacitor doesn’t change that – even Hackaday expects another recap after a few years.
- The Shelly 2.5 is technically outdated: no Bluetooth, no scripting, no Matter, no Zigbee, an ESP8266 with 2 MB flash. Its successors offer all of that.
My advice today: The repair is a good stopgap – for a few cents a dead device runs again until a replacement arrives. But if your Shelly 2.5 fails, you should seriously consider moving to a current generation. I’ve since replaced my last nine Shelly 2.5 with the Shelly 2PM Gen4.
More Hardware Repairs
This repair impressively demonstrates that smart home can be sustainable! The video shows not just the practical implementation, but also my thought process during troubleshooting.
More Repair Guides
- Repairing a Sonoff S20 Smart Plug – the 26-Cent Fix – The same capacitor problem, different device: fixing Wi-Fi disconnects on the Sonoff S20
- Replacing a Tablet Battery Yourself – Save Your Old Device in 20 Minutes! – When the tablet used as a smart home dashboard only works while plugged in
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― Joachim