Red LED Solid

How to Fix It

1. Connect the USB-C cable.

   Plug the supplied USB-C cable into the charging port on the right earcup.
   Connect the other end to a 5V/1A or higher wall adapter.
   The LED transitions to amber/orange when charging starts.

2. Use a known-good cable.

   Cheap or data-only USB-C cables sometimes do not deliver enough current.
   Try a known-good cable from a recent phone.
   If a different cable lights amber, the original was the issue.

3. Try a different wall adapter.

   Laptop USB ports often deliver too little current to charge a fully drained pack.
   Use a wall adapter — phone chargers usually work.
   Confirm the LED transitions to amber within a minute of plugging in.

4. Charge for at least 30 minutes.

   A fully drained Momentum 4 needs time before it will boot.
   Wait at least 30 minutes before pressing the power button.
   Pressing too early may seem like nothing happens — patience matters.

5. Clean the USB-C port.

   Pocket lint accumulates in USB-C ports over months.
   Use a wooden toothpick or compressed air to clear.
   Never metal — that damages the contacts.

6. Reset the headphones.

   If charging works but the LED stays solid red after several hours on a known-good charger, reset.
   Hold the power button for 10 seconds until the LED flashes through several colours.
   Release.
   The headphones perform a soft reset.

7. Contact Sennheiser if dead.

   If 4+ hours of charging produces no LED change and no power-on, the battery has likely failed.
   Within warranty (2 years EU, 1 year US), Sennheiser replaces.
   Out-of-warranty, the battery is not user-replaceable on Momentum 4 — service centre or device replacement.