You run your hand over the aluminium case of your MacBook while it is on the charger, and you feel a light tingle or a buzzing feeling. Sometimes it feels like small shocks, especially when you rest bare arms on the MacBook. If your MacBook gives you shocks, you are right to be alarmed. Usually it is harmless and comes from the plug without earth, but sometimes it is a sign of a faulty charger. This article explains how to tell the difference and what to do.
Blue Apple repairs MacBooks in Amsterdam and tests chargers and charging ports.
Why do you feel it?
A MacBook charger converts mains voltage to a low DC voltage. Chargers without an earth connection let a tiny leakage current reach the MacBook's case. That current is not dangerous, but you can feel it when your skin slides over the metal, especially with dry skin. The feeling disappears when you simply hold the MacBook without moving.
The plug without earth
Apple chargers come with a small plug-in head without earth. On many chargers you can replace it with the long extension cable with an earthed plug, which came with older MacBooks and is sold separately. With earth the tingle usually disappears completely. Also use an earthed socket.
When is it harmless?
- You only feel a soft tingle when stroking the metal.
- It only happens when the charger is connected.
- It disappears with an earthed plug or on battery.
- The MacBook otherwise works normally.
When should you stop?
- You get a real, painful shock.
- The charger or cable is damaged, melted or very hot.
- You smell burning or hear buzzing or crackling from the charger.
- It started after moisture on the MacBook or charger.
Then unplug immediately and stop using the charger. Also read charger or cable broken.
Other chargers
Cheap uncertified chargers often have poorer isolation between mains voltage and the output. The leakage current can then be larger, and the risk of a real shock or damage to your MacBook is greater. Use a charger from Apple or a known brand. See which charger fits.
Connected devices
A small voltage can also reach the case through a monitor, dock or audio equipment, especially if those devices are on different sockets or power strips. Try connecting everything to the same earthed power strip. With audio equipment a hum in the sound can point to the same problem.
How to test it yourself
- Unplug the charger and stroke the case. If you feel nothing now, it came through the charger.
- Connect the charger with an earthed cable to an earthed socket and stroke it again.
- Disconnect monitor, dock and other cables and try once more.
- Try another good-quality charger.
That quickly tells you whether the plug, the charger or another device is to blame.
Static electricity
A single short zap when you touch the MacBook, even without a charger, is usually static electricity from your clothes or carpet. That is harmless.
What we do at Blue Apple in Amsterdam
We test your charger and cable, measure whether there is voltage on the case and, if in doubt, also look at the MacBook's charging section. You hear beforehand what it costs. More on our page about MacBook logic board repair.
Frequently asked questions
Is the tingle dangerous?
With a good, undamaged charger, no. It is a very small current.
Why do I only feel it with bare arms?
Your skin then makes better contact with the metal, and you move over it. That makes the tingle noticeable.
Does another power strip help?
Yes, if it is earthed and you use the charger's earthed cable.
