I was successful in adding a headphone jack to my bike that allows you to control volume, change songs, and navigation prompts through a hard wire 3.5mm jack. Works great. Special thanks to weeT for the wiring diagram. Here is the fix
You will need to connect the new audio cable to three wires located on a the 280A wire harness under the front fairing. I included a picture of my connections. Next is routing the wire. weeT routed his to the phone box on the fairing and used a male 3.5mm audio connection to plug into a Bluetooth transmitter. I ran my cable to the right side of my seat and used a female 3.5 mm audio connection to plug in headphones. To run the cable I had to remove the gas tank, which is pretty easy since my 2016 street glide has a quick disconnect fuel line. I will say pay attention to the routing of the vent and overfill hoses prior to removing so that you will know how to re-install them. There is a plastic cable tray under the gas tank that comes apart so you can easily route the new audio wires. I used 18 gauge wires. I bought the female audio connector from radio shack and soldered the cables, using heat shrink to isolate them after. I just zip tied the audio jack to the frame just under the front right side of the saddle, it is not visibly noticeable.
Hope this helps anyone wanting to use headphones. I use some custom molded headphones from ear inc. that work as hearing protection and are comfortable enough to wear on long rides.
