Audio Systems: 2003 Toyota Nav/Audio system problems, electric antenna, rf input

Question
I have a 2003 toyota Matrix equipped with the Nav/RDS audio system w/ 6 CD changer [under front seat]. Now the radio reception [both AM &FM] just cuts out intermittently. There is apparently no reception because no usual radio text info on presets and just static. It wil do this after an hour in the car. All other functions of system [nav, cd,] work fine. Checked antenna but can't find anything wrong.
Thanks,
Art

Answer
Is it an electric antenna?  If so, the ground on them is often in need of thorough cleaning and reconnecting.  In fact, for any antenna check the ground; clean it and reconnect.

Also, where the antenna connects to the head unit make sure it is a solid connection; pull it out and reinsert a few times to wipe off any corrosion that may have built up.

And, the cable itself can be defective or open circuit.  Check it with an ohmmeter or replace it.

Once you are convinced it is not the antenna or its connection to the head unit then you must suspect the rf input stages to the radio input section of the head unit.  This would involve a rather expensive repair. Or, if it is an intermittent which you can alter by tapping, wrapping or jiggling the unit around it may be a cold solder joint inside the rf section. If you know how to pull the radio, remove the covers and inspect the rf input sections you can touch up any cold looking solder places with a pencil soldering iron.......   Or have a shop do the job for a fee.

Hope this helps.