whinning radio - PeachParts Mercedes-Benz Forum

Dennis Lines · #1 01-10-2004, 04:59 PM

Need help troubleshooting a radio problem. I'm a recent owner of a 98 ml320. With ignition in first postion radio works fine, no interference. In the second position with or without the engine running there is a high pitched whine, especially bad on the AM band not so bad on the FM band. The air conditioner, fan, rear defroster, windshield wipers do not have an affect on the whine. Any suggestions???

Gilly · #2 01-11-2004, 03:45 PM

Possibly a bad antenna amp, or a bad or loose ground for the antenna amp, it's located in the tailgate. As far as yo know the rear (tailgate) glass hasn't been replaced, has it?

Gilly

Dennis Lines · #3 01-12-2004, 11:50 PM

No indication or record of tailgate glass being replaced, the documentation I received from the owner was very thorough. Any suggestions on how to locate the antenna amp in the tailgate and what it should look like? I assume some interior panels need to be removed for inspection and/or replacement. Thanks for the tips!

Gilly · #4 01-13-2004, 05:19 AM

The tailgate panel needs to be removed to access it.
It's on the "passengers" side of the truck (makes it easier to locate because the tailgate will be open, then you'll be looking UP at the tailgate and it gets disorienting). It is a silver box, not really big, like half the size of a pack of cigs.
Only a few wires run to it, and it's secured by an integrated metal tab. Make sure the connections are all tight, including the screw that connects the tab to the tailgate, because the tab serves as a ground. There was a TSB that instructs to make sure there is a good ground contact at the tab, they even suggested sanding a little paint off to make sure you have a good ground contact at that tab.
If you HAD good reception and now it went bad, I'd more suspect the amplifier went bad, hard to tel though, if you come up empty handed I'd get it diagnosed, but this is a good starting point.

Gilly