08-26-2006, 02:11 PM
Join Date: Jan 2005
Location: Brookline, MA
My Ride: ZHP
AM / FM Antenna Amplifier upgrade DIY (when replacing 99-01 radios with 02-05)
This is a DIY for those who have upgraded their 1999 Ė 2001 radio head unit to the 2002 Ė 2005 style. The 99-01 HUís were made by Blaupunkt and the 02 Ė 05 radios were made by Alpine. Many people have swapped 02+ radios into their 99-01ís 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 HUís into the older carís. 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 windowóit is not the shark fin or the bee antenna). The older style HUís 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 driverís 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 #ís for the new antenna amplifiers:
433 MHZ 65256906074
315 MHZ 65256906075
And the link to them on realoem.com:
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). Youíll 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 didnít 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 youíre done!