I also receive practically zero stations on AM. The stations I do recieive are VERY faint, but the signal strength shows five bars. My setup includes an antenna Y-splitter that also serves my Alpine head unit.
The Alpine receives AM stations the same with or without the splitter. The Rio also receives AM stations the same
(albeit zero) with or without the splitter.

I was a little frustrated last night when I drove to the store and couldn't receive the SF Giants game!
GO BARRY!

Mk2 #105 32g blue, w/tuner