iPhone changing audio source when charging in car

Hi Soonerfan2000,

Thank you for using the Apple Support Communities! If CarPlay is not working as expected, the steps below may help:

If you need help with CarPlay

Make sure that your iPhone has the latest version of iOS. If your iPhone is updated to the latest version of iOS, follow these steps — checking CarPlay after each step:

1. Check your connection to your CarPlay stereo:

•If you have a wired connection, try connecting again with a different USB cable to a different USB port if you have one.

•If you have a wireless connection, make sure that Wi-Fi and Bluetooth are enabled under Settings > Wi-Fi and Settings > Bluetooth.

2. If CarPlay doesn't activate automatically, look for the CarPlay logo on your car's display.

3. Restart your iPhone and your car. 

4. Make sure that Siri is on.

5. If your iPhone isn't detected by CarPlay, make sure that CarPlay isn't restricted. Go to Settings > Screen Time > Content & Privacy Restrictions, tap Allowed Apps and make sure that CarPlay is enabled.

6. Go to Settings > General > CarPlay, tap your car, then tap Forget This Car. Then set up CarPlay again.

7. Make sure that your CarPlay stereo is using the latest firmware from the car manufacturer. Check your car's manual for more information.

Hope this helps!

Have a great day.