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AM / FM Antenna Amplifier upgrade DIY (when replacing 99-01 radios with 02-05)

292K views 178 replies 85 participants last post by  max2nice 
#1 ·
Background:

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.


Solution

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 realoem.com:
http://www.realoem.com/bmw/showparts.do?model=ET37&mospid=47720&btnr=65_0481&hg=65&fg=30



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!
 
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#2 ·
Most excellent write up! I like lots of pictures! :)

We have very noisy reception with AM in the stock '99 business radio. If I fiddle with the amp, it affects the performance. Listening to ballgames or talk radio is frustrating. Fortunately for me, this is my wifes car, so AM is a moot point, but I would like to know how to fix it.
 
#3 ·
The AM radios on our cars suck anyhow... Its depressing that they are so poor. My father has a 97 f150 pickup that we use to haul trash to the dump---a totl beather--and it has much better reception than my BMW... Granted it has a 5' antenna too. ;)
 
#8 ·
Great write up sTEVE. you are becoming a PRO at BMW OEM DIY.

I upgraded my 2000 323i Business CD Player with a 2005 version out of a M3.

All I did was bought the attenna adapter. I didn't suffer from any loss in AM or FM reception. All I did was make sure that the COAX cable was tightly secure by the amplifier.

However, if I have problem in the near future I will take your advice and upgrade my amplifer all together.

Great write up! I look forward to our future DIY collaborations
 
#9 ·
Thanks ADA. I had access to a free antenna, so I decided to give it a try to see if it worked--luckily it turned out ot be the same frequency as mine...

Oh, I did a quick test while the antenna was unplugged. I had believed that this antenna amplifier may also be a compensator the Bluetooth phone cradle, so with the antenna unplugged, I snapped my RAZR into the cradle and turned the car on. The RAZR still had the improved reception of the external shark fin--so this amplifier definitely does not power the external cell antenna.

ADA: While I have you on the line here... quick q regarding my tail light issue / bi-xenon headlight issue. I had my good indy shop look at wiring the bio-xenon***8217;s and they told me that the car would not take the programming because it was too old, so it would only take the programming for regular xenon***8217;s... Would it be beneficial to replace my ECU? That***8217;s the main computer that accepts the programming for the tail lights / xenon***8217;s etc, right? Wondering if I had that replaced if it might help.

Anyhow, looking forward to your return to the states. Be safe overseas.
 
#10 ·
Don't mess with replacing your ECU for two main reasons:

1) Too expensive
2) Too complicated since the ECU is the brain of the car.

You can still wire your bi-xenom headlights manually. It will just turn on with your regular high-beam H7. The high-beam xenon will still work (electronic flap) but it will work in conjunction with the H7 high beam. There was a DIY in bimmerfest about this. Basically a guy wired his electronic flapped to his h7high beam.

If i can find the diy i will post it. good luck
 
#13 ·
ADA,
I assume you are referring to Scott ZHP's instructions on biummerfest? Initially my indy shop tried wiring it that way, and discovered that the system would not take the programming. They then figured out that it could be hooked up, but as you said the bi-xenon shutter would be a flasher and the H7 bulb would come onin addition to the bi-xenon shutter on the high beam. I actually left it that way for a while, and unplugged the high beam.. I just turned it back the other day, since my indy installer guy said he was going to investigate how to hook it up properly.


Also, I'd heard of people replacing the ECU on 04 cars so they could have Assist and Bluetooth (as opposed to just BT or Assist). I guess it costs about $900 to do the swap. Should a competent dealer be able to do this?

Thx!
 
#11 ·
Great DIY.... I still have my OEM 2000 cd player in for now and reception sucks cus of my tinted windows. I want to convert the roof antenna for my radio... I have to look into that more.

Charlie
 
#16 ·
Thanks Tom! BTW, I noticed that when the deforster is on and the AM radio is ON, there is no longer the static. That drove me nuts. Anytime I had the AM radio on with the defroster, I heard the loudest screeching static. Thankfully, that seems to have gone away with the new amplifier.
 
#26 ·
Great write-up Steve. I just completed this installation and it only took about 15-20 minutes. As you had explained the bottom torx screw is very difficult to get to. My stubby torx screw driver still wasn't able to get to it because of the angle so i thought i would share how i was finally able to get the bottom torx screw out. I took the torx bit off of my screw driver and used it with a socket wrench to get the top screw off. The socket wouldn't work on the bottom screw so I used the torx bit with a wrench as can be seen in the photos below.

Thanks again Steve for the solution to the crappy reception and also for the write-up!
 

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#29 ·
I had a hard time removing my c-pillar because the damn light won't come off no matter how hard I pry it. Therefore, I was unable to determine the freq. luckily, on the back of my keys, I noticed that the freq was also stamp on there.

any tips on how to remove the light. am I the only one that can;t remove the reading lights on the c-pillar?
 
#31 ·
Damn, how did I miss this thread? :) Great job!

I did the radio change but not the antenna amp with the reception loss, but decided it was a fair tradeoff for the added features. Antenna amps are in the $600CDN range up here. Also I found the reception pretty much cuts out completely when the radio is turned on manually (with the car off). I think this is because the amp (in the older cars) is ignition-powered instead of live/remote.

Also the radio I removed (tape) was Alpine built, not Blaupunkt. I think only the CD players were Blaupunkt.

For those with general poor AM reception, it sometimes can be the coax connector at the amp. If you back it off then retighten, it might fix the problem.

Thanks again for posting the DIY.

Mark
 
#38 ·
Wow, I searched and searched for this information and even misunderstood some of it myself based on what I read in the Bentley manual - great post! :)

I just ordered the adapter cable for now. I don't listen to AM at all but I still want it to work, but I'll see how I go before spending £150 on a new amplifier!
 
#40 ·
i realize this is like months later on this thread, but of opposed to replacing the antenna amplifier for $200ish, could you not simple attach the extra wire for the antenna amp to a 12v switched source such as the white wire in the radio harness? I would think that would then turn on the 99-01 antenna adapter. My understanding was that the "extra" wire was to simply send a signal to turn it on when you switched from cd or mode over to the radio function.
 
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