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I am able to get AM radio. I click on TuneIn then browse, then local stations. You will see AM and FM stations you can choose from and add to favourites
Check the TuneIn Radio app for your local AM stations. If they're not there, then you can't listen to them in the Tesla.
Also, the TuneIn app for smart phones sometimes has stations available that aren't available on the Tesla's TuneIn. If they're available on your smart phone, then you could stream them to the Tesla via bluetooth. However, you will be using your cellular data.
One final thought. Sometimes AM stations are broadcast on a local FM HD Alternate stations, which can be tuned in the Tesla. You could check this as well.
Technically, it should be possible to add an AM receiver and input the audio into the Tesla's sound system. Don't quite understand why the Tesla doesn't have AM as a lot of receiver chips have both signals available.