Will not switch between devices about a2dp-connect2 HOT 2 CLOSED

This may not be possible.  Generally you will need to edit the Bluetooth 
settings for these devices such that they do not compete for a profile.  If 
your car does not support the A2DP profile (often the case) this widget won't 
do anything for it.  If you don't want the Nolan to do handsfree (since the car 
does that) you can disable that profile in Android settings.

Your scenario is a common one.  I recommend instead using one of my other apps 
called A2DP Volume.  It will see the car connect and then automate the 
connection to the A2DP Profile on your streaming device.  Then you don't have 
to touch anything.