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One of the first projects new BMW owners perform on their car is to remove and replace their stereo head unit. I know that if I buy a car that has a weak stereo unit, it's one of the first things to go. The factory BMW head units (manufactured by Alpine) are best described as barely adequate - the technology is at least 10 years old in most cases, and the units also seem to have a rather high failure rate after many years of use (Figure 1).
The good news is that the replacement process is relatively easy, providing you have the right information, and the right parts. First, disconnect the battery. The radio harness has constant voltage supplied to it, and you don't want to accidentally blow any fuses or damage any electrical components. Begin by flipping open the small flap on the OEM head unit (Figure 2). Underneath, you will find a funky 5-sided bolt on the inside (Figure 3). I guess BMW thought it would be more difficult to remove the stereo if the bolt was a non-standard one. Well, my standard hex tool fit right in there, and was able to remove it with no effort involved (Figure 4). If your bolts are more securely tightened, then you may need a specific five-sided tool for the task. After the bolts are loose, you should be able to simply pull the unit out by hand (Figure 5).
On the back of the unit, there is a large black connector, and a smaller antenna connector (Figure 6). Remove the antenna connector by simply tugging on it. The large black connector has a retaining strap that needs to be released prior to pulling it out of the radio (Figure 7 and Figure 8). Don't force the connector, or you may break it.
In order to install your new radio, you will need a BMW cable adapter (Figure 9). This adapter plugs into the factory connector and has leads on it that you can then connect to the leads or connector on your new radio (Figure 10). You can cut the OEM connector off and tap directly into the factory harness, but I strongly caution against this - it's best to use the adapter cable. I put some spade connectors on the ends of the harness adapter, and the connector that plugged into my new radio. The adapter harness is shown on the left in Figure 10, and the new harness that came with the new radio is shown on the right.
In general, most wire harnesses are configured according to an industry standards which is shown in the following table:
|Red||12 Volt Switched Power|
|Yellow||12 Volt Constant Power|
|Green||Left Rear Speaker Positive|
|Green/Black||Left Rear Speaker Negative|
|Violet||Right Rear Speaker Positive|
|Violet/Black||Right Rear Speaker Negative|
|White||Left Front Speaker Positive|
|White/Black||Left Front Speaker Negative|
|Gray||Right Front Speaker Positive|
|Gray/Black||Right Front Speaker Negative|
Figure 11 shows the back of the new head unit, with connectors for the harness connector included with the unit, connectors for an external amplifier, and an antenna connector. Plug the harness adapter into the factory connector, and then plug the harness into the back of the head unit and connect all of the spade connectors, as shown in Figure 12.
On this particular head unit, I found that the antenna jack on the back of the unit was not compatible with the one in the factory harness (Figure 13), so I needed an antenna adapter as well (Figure 14). Plug the adapter into the back of the unit (Figure 15 & Figure 16), and then you should be able to plug the antenna cable into the unit (Figure 17). With the new head unit wired up (Figure 18), reconnect the battery, and turn it on to test it (Figure 19). If all of the speakers, radio, and lights work, then install the radio bracket into the center dashboard. This is the bracket that comes with your new unit, and typically has tabs that you bend into place once you position the bracket. When the bracket is secure (Figure 20), simply slide the radio into its spot on the center dashboard. Be careful though - most of these units are designed to be easy to install, but very difficult to remove, so make sure that everything works before inserting it into the dashboard.
Well, there you have it - it's really not too difficult at all. If you would like to see more technical articles like this one, please continue to support Pelican Parts with all your parts needs. If you like what you see here, then please visit our online BMW catalog and help support the collection and creating of new and informative technical articles like this one. Your continued support directly affects the expansion and existence of this site and technical articles like this one. As always, if you have any questions or comments about this helpful article, please drop us a line.