Ii'm posting this here for 2 reasons:

first - I couldn't see any Fenix 3 related forum

second - this post is mainly to confirm that Polar H10 heart rate sensor can connect with Fenix 3 Sapphire. I searched the internet for resources that  answer my question about whether it will connect or not. so i ordered the H10 and tried it yesterday, it works just fine.

You might ask me why am I using the Polar H10. I have been always a loyal customer to Garmin and will continue to be. But I believe their HRM Tri should really get a complete redesign and enhance it's quality. I bought 3 units in the last 4 years, it would simply die when I replace the battery. I tried all the mentioned troubleshooting steps, but I couldn't.

However, thanks to Garmin, they are going to replace my unit. It's on the way to be delivered to them, so they can send me a new one.

I hope this post help people like me who are still using Fenix 3 because of one simple reason: It just works very well !! I still can't justify the upgrade to Fenix 5 or 6, although I wouldn't mind if someone gave it to me as a gift! LOL