FM Antenna Amp / Radio question - E46Fanatics E46 BMW Social Directory E46 FAQ 3-Series Discussion Forums BMW Photo Gallery BMW 3-Series Technical Information E46 Fanatics - The Ultimate BMW Resource BMW Vendors General E46 Forum The Tire Rack's Tire Wheel Forum Forced Induction Forum The Off-Topic The E46 BMW Showroom For Sale, For Trade or Wanting to Buy

Go Back   E46Fanatics > E46 BMW > General E46 Forum

General E46 Forum
This is the place to get answers, opinions and everything you need related to your E46 (sedan, coupe, convertible and wagon) BMW!

Thread Tools Search this Thread Rating: Thread Rating: 9 votes, 5.00 average. Display Modes
Old 04-02-2009, 10:47 AM   #1
Registered User
Join Date: Sep 2008
Location: Sunderland
Posts: 119
My Ride: E46 330i Sport
FM Antenna Amp / Radio question

Ive recently replaced the original casette BMW Business head unit in my 2000 Convertible. I have installed a 2003 CD BMW Business head unit in its place.

All works OK - but the quality of the FM radio has reduced. I am lead to believe that this is becuase the thin coax cable that is now not connected (because the new head unit has no place to plug it) was used to suplpy power to the amp (located in the boot) and this is the reason for the poor signal quality.

My questions are can I provide power to this unit some other way? Or do I need to replace it for a 2003 unit? (and if I do, how is it then powered?)

Help much appreicated as ever
gphillips is offline   Reply With Quote
Old 04-02-2009, 10:55 AM   #2
Registered User
Join Date: Dec 2007
Location: NJ
Posts: 146
My Ride: 2001 325ci
I'm having the same problem someone please help
Spaniardstud is offline   Reply With Quote
Old 04-02-2009, 11:43 AM   #3
Registered User
Join Date: Jan 2005
Location: St Louis
Posts: 614
My Ride: 2006 325ci vert
I replaced the Business cassette in my 2000 E46 with a 2003 Business CD headunit and my FM reception is great. Because you have to use an antenna adapter to get your present antenna lead to properly connect to the new radio, you have to ensure that the connections are tight. A loose antenna connection could lead to poor reception.

2006 325ci vert
Steve330ci is offline   Reply With Quote
Sponsored Links
Old 10-14-2009, 06:55 PM   #4
Registered User
Join Date: Jul 2007
Location: Burlington, NJ
Posts: 154
My Ride: 128i, 330i, Z3 2.3
where do you buy the antenna adapter??
amancuso is offline   Reply With Quote
Old 10-14-2009, 09:37 PM   #5
Registered User
Join Date: Nov 2008
Location: Westchester, NY
Posts: 6,342
My Ride: 335i xDrive Deep Sea
Year: 2011
Model: 335i
Transmission: Steptronic
Send a message via ICQ to delmarco Send a message via Yahoo to delmarco
You have to replace the antenna with the new post 9/2001 self power antenna!

The pre 9/2001 antenna/radio combo use a power cable that runs from your old pre 9/2001 radio to the old pre 9/2001
antenna and powered it. When you upgraded your radio with the new post 9/2001 radio your old antenna LOST all power from the radio.
So hence the reduction or elimination of FM/AM reception.

YOu have to upgrade the antenna to the newer self powered version!
delmarco is offline   Reply With Quote
Old 10-14-2009, 09:46 PM   #6
Registered User
Join Date: Nov 2008
Location: Westchester, NY
Posts: 6,342
My Ride: 335i xDrive Deep Sea
Year: 2011
Model: 335i
Transmission: Steptronic
Send a message via ICQ to delmarco Send a message via Yahoo to delmarco
It's all been explained before!


Originally Posted by sna77 View Post

This is a DIY for those who have upgraded their 1999 - 2001 radio head unit to the 2002 - 2005 style. The 99-01 HU's were made by Blaupunkt and the 02 - 05 radios were made by Alpine. Many people have swapped 02+ radios into their 99-01's to take advantage of the increased functionality of the newer style radios (Sirius, AUX input, OEM iPod adapter). NOTE: Sirius requires an 03+ radio.

Anyhow, the one caveat of doing this is a noticeable loss in AM / FM reception when putting the newer HU's into the older car's. The reason for this is because in 2002, BMW changed the type of antenna in the car (NOTE: In all coupes / sedans the antenna is in the rear window-it is not the shark fin or the bee antenna). The older style HU's have 2 antenna connectors on the back of the radio, and the newer radios only have 1. There is an OEM antenna adapter available that converts 1 of the 2 adapters, allowing basic connectivity of a newer HU to a 99-01 car. The unused wire (I believe) is used to power something known as the antenna amplifier, which is located in the rear driver's side C-Pillar. Without that wire connected, there is a significant loss of reception in the AM / FM radio.


If you want to upgrade to the newer style radio and not suffer any radio reception loss, you must replace the antenna amplifier in the rear C-Pillar. This amplifier also is responsible for the keyless entry in the car, so you may benefit from increased range with the new amplifier as well.

Important: There are 2 different frequencies used for the keyless entry system (315 MHz and 433 MHz). You must first determine which frequency you have before you order an new amplifier. Luckily, your existing amplifier is stamped with the current frequency, so you simply need to pop the C-pillar off and do a visual inspection to determine which part you need to order from the dealer.

Here are the relevant part #'s for the new antenna amplifiers:

433 MHZ 65256906074
315 MHZ 65256906075

And the link to them on

OEM Antenna adapter:

Comparison of Old vs. New antenna amplifier:

Once you have ordered the proper antenna amplifier (circa $200 from the dealership), installation is pretty easy (takes about 20 minutes). You'll need a flat head screwdriver and a T20 torx screw driver as well. If you can find a stubby T20 torx, that would be very helpful, as the screws are at a hard angle to unscrew.

Step 1: Remove map light. Gently fit a thin flat head screw driver on the top of the map light and pry it out. It will pop right out. Disconnect the light and set it aside.

Step 2: Remove C-Pillar. Its actually easier than it looks. Just reach your hand into the opening where the map light is, and pull. There are 2 plastic pieces holding the C-Pillar on. They should give way, then pop out.

Instructions from the TIS on removing C-Pillar:

Step 3: Remove old antenna amplifier. Use the T20 torx screw driver to remove the old antenna amplifier. I didn't have a stubby torx, and was unable to unscrew the bottom screw, but was able to break the bracket off by bending the amplifier back and forth a few times. No worries, as the one screw holds the amplifier in just fine. Once the amplifier is unscrewed, unplug all the connectors.

Step 4: Connect the new antenna amplifier. I found it easiest to connect all the wires first, then screw the new amplifier into the car. You will notice that there is an extra wire now (this is the wire that powered the older style amplifier that terminates at the HU. It is OK to just tuck this wire under the rear deck. This wire is now connected to nothing at both ends.

Step 5: Verify that everything works. Turn the car on and make sure that both AM / FM radio work. Turn the car off, and verify that the keyless entry works as well. Once everything is tested, simply push the C-pillar cover back on, reconnect the map light, and you're done!
delmarco is offline   Reply With Quote
Old 10-15-2009, 01:38 PM   #7
Registered User
Join Date: Nov 2008
Location: Westchester, NY
Posts: 6,342
My Ride: 335i xDrive Deep Sea
Year: 2011
Model: 335i
Transmission: Steptronic
Send a message via ICQ to delmarco Send a message via Yahoo to delmarco
Basically when you make the upgrade to ANY E46 Business CD unit made after 9/2001 (2002 to 2006) you have to get the newer self powered antenna AND the radio's antenna adapter.
Lots of folks tell you it's just plug and play and it is partially true the newer radio will plug and turn on but in theory it will NOT plug and play FM/AM etc if you don't get the newer antenna parts.
delmarco is offline   Reply With Quote
Old 10-01-2010, 03:22 PM   #8
Registered User
Join Date: Apr 2009
Location: spain
Posts: 25
My Ride: 330ci cabrio
I have te same problem retrofiting a new gen radio (bm54) from old gen radio (bm14) on e46 cabrio from 08/2001

There is any way to increase old 12V connector for the amplifier to operate without having to buy a new one?

Thanks all
lynks is offline   Reply With Quote
Old 07-19-2011, 11:54 AM   #9
Registered User
Join Date: Apr 2010
Location: Amsterdam, The Netherlands
Posts: 20
My Ride: Bmw e46 328i
What about the antenna amplifier from 99' models, I found one on the German eBay and it doesn't have the power connector. So we can says that it's also self powered?
DutchPlayer is offline   Reply With Quote

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Censor is ON

All times are GMT -5. The time now is 10:17 PM.

Powered by vBulletin® Version 3.8.8
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
(c) 1999 - VerticalScope Inc. All rights reserved.