ios 12.1 Volume buttons not controlling Bluetooth

I'm going to attempt to write this post so someone else can quickly find what it took me hours to google for.

Or myself, when I forget in a couple years.

Date of post: 11/10/2018

Phone: SE

IOS Version 12.1

Keywords: iPhone volume buttons Bluetooth sound level

Problem: Bluetooth earpieces, headphones and external speakers would no longer control sound output based on volume buttons on phone or sound bar sliders.

Some brands would only work as ON/OFF at the extreme ends of the scale. (Parrot)

Some brands would toggle sound on and off with every other push of the volume buttons, but always the same low level. (Plantronics)

Still other brands would only increase volume on the headset alone.

For all brands, any pressing of the volume buttons on the phone, or adjustment of either the device slider or music volume slider would set the device itself back to minimum volume, requiring fumbling with the controls on the headset again.

Another odd symptom was that only 1 song would play, and then the volume would return again to the lowest level and be basically muted.

Solution: Even though this was also affecting call volume (where I first noticed the problem) the setting at fault is this: (I'm not sure if this got set during an update, or if it was my mistake)

Settings App >> Music

Scroll down within the Music settings to the PLAYBACK Section.

1. Click on Volume Limit, slide the slider control all the way to the right for maximum volume. When you go back to the previous screen you will see Volume Limit is now Off. (Note what setting you had here)

What was happening is that when the phone sent any command for a change in volume, the IOS first checked the maximum volume setting. If your volume limit somehow got set to the minimum value all the way to the left, the phone's operating system dutifully set your volume on your device to 0 because that was the maximum allowed.

This effectively defeats all volume control from the phone for your headset or Bluetooth device.

Before changing the other settings, see if your headset or other device will now change volume with the iPhone controls, both buttons and sliders.

2. For loudest maximum sound available, I found either Off, Flat or Late Night to be the best. I prefer Flat.

3. Sound Check. Off for maximum sound is the setting I prefer.

Hope that saves you (or me) some grief.