ML 320 Radio Problems - PeachParts Mercedes-Benz Forum

Litton · #1 11-05-2004, 04:26 PM

I have just purchased a '98 ML320 and noticed that the AM radio doesn't work worth a hoot. FM is OK, weak but OK, and the CD changer works fine.

On AM, all I can get are the strongest stations or a lot of ignition noise. I have the stock Bose unit. Any words of wisdon for this new ML owner.

Actually, I just went out and looked again, and I don't even know where the antenea is located.

Gilly · #2 11-05-2004, 07:43 PM

Antenna is part of the rear window. If the rear window was replaced, it's possible that the reception will never be as good as it was.
A few problems I've found in regards particularly to AM reception (you must like talk radio too!), it that the coax connector on the antenna amplifier may be a little loose, OK that's one possiblity, secondly the factory had a bulletin out in regards to removing the amp, sanding some of the paint off where the amp mounts to the metal (to get metal on metal contact) and reinstall the amp and then painting the area to prevent rust. You could also make sure the coax is tight behind the radio.
Oh, the antenna amp is behind the tailgate panel (interior trim).
But this definitely was a common complaint especially in 98-99 on the ML. There may have been other suggestions in the bulletin, as I recall. Making sure the screw is tight holding down the amp is the other.
Gilly

Litton · #3 11-07-2004, 09:44 AM

Thanks for the advice. I will try an get at the amp today. Any hints as to how to get the tailgate panel off???

On a side note, I found a little cable hanging down on the passanger side that looks like it may come from the radio. It sorta looks like a skinny coax with a tiny plug on the end. I will try and get a pic.

Jim W. · #4 11-21-2004, 08:42 PM

In the past we have had severe AM radio interference in our M-Classes. One of the preferred stations is a quality one about 100 miles from our home which puts us in a fringe reception area susceptible to interference. Other vehicles parked next to the ML did not have the interference, however, including our 1978 300SD. Our 1998 ML had the radio replaced and extensive diagnosis at the dealer with little improvement. The tech at the dealer said it sounded like a grounding problem. When we bought the 2000 ML320 we had the same problem and again the dealer did a lot of work trying to find the problem, including a new antenna amplifier in the cargo door and cleaning up all the connections in the door. None of it helped much. The interference was especially pronounced when accelerating or using power options like the windows or outside mirrors.

I have found what has worked the best and have delayed posting this until I had time to use the vehicle and verify the fix will last. Lately we replaced the battery in the 320. The negative cable is grounded to the chassis at a bolt on the firewall. There are two other wires attached to the bolt also. I removed the nut and cables from the grounding bolt, used jumper wires to maintain electrical connections, and burnished the bolt, contact side of the nut, and wire connectors. They were then coated with electrical conductivity grease and reinstalled. The result is that the radio is working at a very acceptable level now. It appears grounding was the problem and the fix was easy.

There is a service notice sent to dealers about this problem and a resource from another forum is going to send me a copy this coming week. I will pass it on.

By the way, your post was earlier this month, have you done anything about the problem since?

Jim W.

sunedog · #5 10-22-2006, 05:59 PM

I suffered from weak reception as well in my 99 ML 320. Today I cleaned up the ground points on the firewall as Jim W suggested but no improvement.

So I took off the tailgate panel and *voila* found a broken wire from the antenna amp to the rear glass. I'll bet that was the problem.

15 minute project and now I can listen to all my favorite stations.

Thanks for the tips and this great forum.

G-Benz · #6 11-11-2006, 06:11 PM

...been following this thread as my radio reception had suddenly deteriorated for no apparent reason. Checked ground on firewall as mentioned but no change. Noticed reception worsened when tailgate was lifted, so I believe that the problem resides there.

Any tips on how to remove tailgate panel(s)?

sunedog · #7 11-13-2006, 08:25 AM

A search of this forum will probably get you more comprehensive info, but here is a little from my experience:

- Remove two plastic screw covers and then screws on the top sides of the panel near the glass.
- I don't remember if you have to remove the screw holding the door handle trim, but I did remove it last time I took off the panel.
- I believe the rest of the process is to just carefully pop loose each plastic trim connector. Don't know what these are called. They are plastic rocket shaped things that pop into mating receptacles in the tailgate. I used my hands/fingers to pull them out. Pull the trim panel away from the tailgate a little after you have removed the two screws and you can see between the trim panel and the tailgate to locate these connectors. There is probably a tool to do it without breaking them.

G-Benz · #8 01-01-2007, 10:27 AM

A recap of what was found with my antenna reception issues:

Indie discovered severed coax wire just near the headliner and hatch area...apparently due to stresses and cable fatigue from being kinked at the hinge point at the hatch. Our guess was that years ago, when the headliner was removed to reglue the sound deadener panel, the cable was not routed properly upon reinstallation, leaving it exposed to (ulimate) damage.

Fix required about $2 worth of parts...cost of labor and diagnosis is another story...