Audio Systems: Poor reception on AM, window tinting film, poor reception

Question
I have a 2005 Prius. About 4 months ago I began experience very poor reception on the AM portion of the car's radio.  FM works fine.  I took the car to a Toyota dealer who pulled the radio, but didn't change anything.  However, I noticed that the reception was much better when I got the car back.  About 2-3 weeks after, the AM reception started going bad again, and is now extremely poor.  Occassionally, the AM will be pretty good, but the overall trend is bad.

Answer
did you add window tinting to that vehicle  sometimes window film in the back window stops the fm/am signal
there is also a msll amplifier in the back next to the window that can be damage check that i am sorry i can not help you more

i was working on a 07 avalon and after replacing the radio and sending the car to the dealer a few times
removing the window tinting film solve the problem
some of them have metal parts on the film
good luck