Very weak FM Signal from Navagation Radio

[larryl]

2008 OEM Nav radio on Danaili has very weak signal on AM / FM only. Everything else works fine. The antenna is built into back side window and seems to be connected at least from outside view.
Signal can be non existant for stations I know have strong signal and then for some reasom after 5 -10 minutes come in clear and seem to stay that way until maybe the next day. Anyone have an idea how to fix this.

BTW we are 2nd owners so I have no idea if this has happened since new.

 

[KWIKNVA]

Basically the same issue here. I have a 09 Yukon Denali. I'm getting one station with a decent signal. All the other stations are poor if not there at all. This must be a common GM issue cuz my 02 Sierra basically has the same issue but worst. I replaced the factory radio with an aftermarket head unit. Both stock and aftermarket have poor signal. I was going to replace the antenna in the 02 but now the 09 has the same issue as well. My wife's MDX has no issues. I doubt it's our location.

 

[Chiggy]

Probably going to have to post this in the 07 and up section. Here we all have antennas mounted in front of the windshield on our 00-06's. A common mod is to unbolt it and hide it under the hood running along the fender. Our wiring and radios are different. But someone might be able to help.