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BMW Poor Radio Reception DIY Repair, AM and FM, E46 3-Series and Other Models

September 8, 2011

A common complaint on later model BMWs (those with the amplified “diversity” antenna systems using the rear window defroster grid, as well as “shark-fins”) is poor radio reception.  This problem can show itself on both the FM and AM bands and is typically progressive.  The cure is relatively easy to implement.  Check the steps below, shown on a 4-dr E46 model (3-series 99-05).  Other models will be similar.  The applicable Bentley repair manuals will detail the C-Pillar trim panel removal on other BMW models.

DeoxIT:

Other DeoxIT products:

Non-Marring pry tools:

Bentley repair manuals:


PROCEDURE:

1)  On the driver side (left side): Pull back the door gasket, along the C-pillar.

2)  Use a non-marring pry tool to pry the C-pillar trim cover loose.  There are two clips at the upper end of the cover (see the following photos).  Unplug the light harness plug and then pull the cover upward to fully remove it.

3)  You now have access to the antenna amplifier and the window grid connections.

4)  Unplug and remove the window grid connector harness.

There is one snap clip at the upper end of the window grid harness plug.  Carefully pry the clip away and push the plug assembly upward to remove.

Connector plug on window with harness plug removed.

Window antenna harness plug.  Clip is show at pinky finger.

Disconnect window harness from amplifier.

Window harness removed.

4)  Disconnect the antenna output and power connector plugs from the amplifier.

5)  Apply the DeoxIT drops to each terminal connection on both ends of the window harness and each of the antenna and power terninals.

6)  Reassemble the window connector harness and the output and power plugs.  Reinstall the C-pillar and the door gasket.

7)  There is another unit under the passenger side (right side) C-pillar.  This is a radio frequency trap, or filter.  Perform the same work with the DeoxIT on this unit.

6 Comments
  1. Jason permalink

    If it’s that simple, why can’t car manufacturers do it?
    Is it too fiddly or is it because they can sell more products when car buyers want to get better reception.

    • Otto permalink

      The oxidation of the contact terminals is a progressive issue. At initial assembly, all is fine. As the vehicle ages, the electrical contact terminals oxidize and this reduces the electrical contact. The radio antenna signal is very low voltage and current. Therefore it is quite susceptible to interference due to the oxidation.

      The DeoxIT will not only clean the terminals, but it leaves a protective coating to prevent future oxidation or corrosion.

  2. Dean Curtis permalink

    My 1996 328i Convertible has the same problem (I think). FM reception is especially bad. It sure would be nice to be able to pull in some good old FM tunes while driving down the road with the top down. Is there a similar fix? I have the “whip” antenna on the back next to the trunk. Do you think it’s the connections? Could it be the amp? Thoughts?

    • Otto permalink

      The antenna on your E36 convertible (as well as the 318ti and the Z3 models) is different from the defroster grid applications. However, if you are experiencing reception problems, then we would suggest that you perform a similar DeoxIT application. You will have the connection where the antenna mast screws to the amplifier unit and the connection from the amplifier to the antenna cable (inside the trunk, behind the side trim panel).

  3. Noel Hernandez permalink

    I have been going insane the last year trying to listen to the radio with the defroster on…I am glad you guys posted this. I appreciate you folks identifying these common problems so we can fix them. Thank you.

    • Otto permalink

      Let us know if this DIY helps with the defroster interference.

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