I believe some devices just don't have the feature because my GS3 didn't do it as well. I researched it and found out that it's a Samsung thing. Yesterday I tried it out on my G3 and it didn't work. I had to reconnect with the device in order for it to pick it back up. Now if I leave the vehicle and turn off blue tooth and return to the vehicle and turn it back on then it will connect, but if I leave blue tooth on and return it will not play through the vehicle until I manually connect the BTC450.
I have a built in infinity 7.1 sounds system from Kia. The issue is not the system nor the phone. When you turn Bluetooth ON on the phone, it'll go visible and search for devices for around a minute then it'll go invisible and stops searching. The reason it stops searching is to save battery. Now, if you start the system in the car, and you turn Bluetooth on, they'll connect, because the phone will be visible, and it'll be searching for devices, it'll see the car system and recognize it's paired, so it'll connect.
Now if the car system is off, and the phone Bluetooth is on, and you start the car system, it's not going to connect. Because the phone is saving battery and the Bluetooth is invisible and not searching, so it's not going to see the car system. It happened with my s2,s3,s4,s4 & now with the G3.
I only use Bluetooth when in the car and sometimes with my home sound system.
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