Troubleshooting Apple Watch and External Heart Rate Monitors

The Apple Watch is a very powerful wrist-mounted personal communications device, but with that great power comes great responsibility for battery life.

Whilst the internal HRM is satisfactory for some activities (sleep, background, and supposedly running), like all wrist/optical sensors its accuracy is challenged when the wrist is being used, for example when cycling or climbing.

Whilst attempting to use my Polar H10 with my Ultra to track climbing with Redopint today, I noticed the watch would connect to the HR sensor in the Bluetooth settings, and then disconnect. Redpoint showed that it was waiting for HR data, but not recording any. I was able to resolve this after two actions:

1. I replaced the CR2032 battery. I don’t know if it was low, but it seemed like a safe bet.

2. I opened the Health app on my phone, and revoked all permissions that Redpoint had, and granted them again.

After both of these, normal HR service was resumed. I suspect that step 2 would have been sufficient, and was able to repeat the step with another app, Workoutdoors. I tried to record an activity (hanging laundry, naturally) with Workoutdoors, but noticed that like Redpoint earlier it had not HR data. I opened the Health app on my phone again, and noticed this time that Workoutdoors had no permissions granted. Upon granting it permission to access all data, the problem was solved: over 10m, I observed a stable connection to the H10.

Interestingly both of the problems presented after migrating to a new phone: I believe there’s a bug in the phone migration process around Health permissions, but it’s an easy fix.