Radio Antenna Coil - GM 13293348

[Linthead]

2013 2SS Coupe, My Link with Nav & Sat Radio



Until today, I thought the FM antenna on my 2013 SS coupe was part of the roof mount shark fin but that is incorrect. I have been noticing that when I turn on the rear defogger, my FM radio signal strength would drop. A station playing clear an loud would drop in volume and act as a weak station when I turned on the rear defogger. I decided to check if I had a powered FM antenna and rear defogger that shared the same power source and it was a voltage drop issue. After I removed the rear deck cover, I found that just before the 12V power goes into the rear defogger grid on the passenger side, it passes through an odd component (GM 13293348) that is identified as an antenna coil (it is discontinued now). There is no signal connection on this component so it may just be a power filter for the defogger grid. No power is fed to this component unless the rear defogger is on. The radio works fine when no power is applied (no defogger). I did not try bypassing this component and running the 12V directly to the defogger grid to prevent possible damage to anything. The FM antenna signal connections are at the top corner of the rear glass on the driver's side. The top 5 lines on the rear glass is the AM/FM antenna. The only common connection for the AM/FM antenna and the defogger grid is the ground connection for the defogger on the drivers side of the the rear glass. Does anyone understand what the purpose of GM 13293348 is? If this component is not the problem then the electrified defogger grid must be interfering with the FM signal reception.

[pcguy2u]

No absolutely helpful info here, but some insight:



The radio sends 12v on the center core/conductor which powers the corresponding component on the drivers side; that's the same component that has a 9v battery like connector that plugs into the defroster grid.


Not sure how you determined there is an isolated connection to the top five line???


Very mysterious setup, but I am about to find out if this setup works in my restomod project - link below. Have had no results so far, but I'm hopeful.


Nick

[Linthead]

Originally Posted by pcguy2u

No absolutely helpful info here, but some insight:

The radio sends 12v on the center core/conductor which powers the corresponding component on the drivers side; that's the same component that has a 9v battery like connector that plugs into the defroster grid.

Not sure how you determined there is an isolated connection to the top five line??? I just reviewed the layout on the glass.


Very mysterious setup, but I am about to find out if this setup works in my restomod project - link below. Have had no results so far, but I'm hopeful.


Nick

I did more testing today. With the car running, I powered the defogger grid with the positive battery post in the trunk and it still reduced the FM signal strength. I restored the normal connections and checked for operational voltages. There is no voltage present at the two connections where the antenna wire connects to the grid on the glass with the radio ON and defogger OFF. With the defogger ON you can see a .43v dc potential between the defogger grid ground and the antenna shield ground connection at the top of the glass. Also, the defogger ground wire that connects to the metal rear deck gets exceptionally hot. The wire gauge of the ground wire is smaller than the wire that feeds the power to the defogger grid. I am going to replace it with a larger size that can carry the load without getting hot and see it that improves the FM signal situation. My last option will be to provide the antenna wire shield its own ground connection to the body.