Maintenance of your M400

Like any electronic device, the Polar M400 should be kept clean and treated with care. The instructions below will help you fulfill the guarantee obligations, keep the device in peak condition and avoid any issues in charging or syncing.

Please note that we have removed the rubber cover from the USB port in the latest version of M400. This was done to make the drying of the USB port easier and more effective. These maintenance guidelines can be used for both the new M400 without the rubber cover and the previous model with the rubber cover.


The USB cable must be connected carefully to avoid damaging the device's USB port.

Keep the device's USB port clean to ensure smooth charging and syncing.

Keep the USB port clean to effectively protect your M400 from oxidation and other possible damage caused by salt water (e.g. sweat or sea water) and dirt. This way you ensure smooth charging and syncing.

The best way to keep the USB port clean is to rinse it after each training session as follows:

1. Lift the rubber cover off the USB port.

2. Rinse the USB port with lukewarm tap water.

The USB port itself is water resistant and you can rinse it under running water without damaging the electronic components.

3. After rinsing, leave the cover open for a while to let the USB port dry. Do not charge the M400 when the USB port is wet or sweaty.

When using the USB port, check that there is no moisture, hair, dust or dirt on the sealing surface area. Gently wipe off any dirt. A toothpick can be used to remove hair, dust or other dirt from the connector cavity. Don't use any sharp tools for cleaning to avoid scratching.

You can wash the device with a mild soap and water solution under running water. Do not use alcohol or any abrasive material such as steel wool or cleaning chemicals. If you don't wear  the device 24/7, wipe off any moisture before storing it.

Do not leave the device in extreme cold (below –10 °C/14 °F) and heat (above 50 °C/120 °F) or under direct sunlight.


Keep your training device in a cool and dry place. Do not keep it in a damp environment, in non-breathable material nor with conductive material. Do not expose the training device to direct sunlight for extended periods.

Store the device partially or fully charged. The battery slowly loses its charge when it is stored. If you are going to store the device for several months, it is recommended to recharge it after a few months. This will prolong the battery life.

Heart rate sensor


Detach the connector from the strap after every use and dry the connector with a soft towel. Clean the connector with a mild soap and water solution when needed. Never use alcohol or any abrasive material (e.g. steel wool or cleaning chemicals).


Rinse the strap under running water after every use and hang to dry. Clean the strap gently with a mild soap and water solution when needed. Do not use moisturizing soaps, because they can leave residue on the strap. Do not soak, iron, dry clean or bleach the strap. Do not stretch the strap or bend the electrode areas sharply.

Check the washing instructions on the label of the strap.


Dry and store the heart rate sensor strap and the connector separately to maximize the battery lifetime. Keep the heart rate sensor in a cool and dry place. To prevent snap oxidation, do not store the heart rate sensor wet in non-breathable material. Do not expose the heart rate sensor to direct sunlight for extended periods.


During the two-year guarantee/warranty period we recommend that you have service done by an authorized Polar Service Center only. The warranty does not cover damage or consequential damage caused by service not authorized by Polar Electro. For further information, see Limited International Polar Guarantee.

For contact information and all Polar Service Center addresses, visit and country-specific websites.

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