fēnix® 3 HR: A Non-Destructive Teardown | by Red Turtle | Personal Notes on the Garmin® fēnix® 3 HR | Medium
Heart-Rate Monitor
Garmin Fenix 3 Hiking GPS Review - HikingGuy.com
Garmin Fenix 3 For Step Counting and Running - Sundried
PSA: Look at the heart rate sensor of your fenix 5. Has it cracks like mine? If yes, it's a common problem. Send it to Garmin and get a free replacement. Do