Replacing HU850 with Aftermarket head unit walkthrough | SwedeSpeed

So after combing these forums, and going over and over looking for solutions, I decided to bite the bullet and go for doing an aftermarket head unit install in my ’05 VR with the HU850. This one is notoriously tricky, as it has the factory amplifier in it that needs a 6 pin DIN adapter to work properly. Additionally, center channel is tough because that one is not driven by the amp for whatever reason. In doing this, I wanted to accomplish a few things:

1. Maintain factory amp and independent speaker channel sound
2. Not lose the center speaker
3. Maintain an “OEM+” look to the center console with the new unit in
4. Maintain steering wheel controls.

I did a bunch of research and I will link the main threads I used below:

Main stereo replacement thread This one is great, because it has all of the pinouts of the original connector on the factory wiring harness. Additionally, if you want to wire in backup camera, etc that is in this thread. For now I didn’t do that, but my stereo has those connections so I may do it in the future.
Head unit reddit thread This one is useful to show what the “OEM+” look can look like, which I didn’t go for, but may down the line. Reasoning is below.
Alternator whine solution This one is great if after you wire everything up, you are getting alternator whine. I did, and my solution ended up being post #25 by “Arch Stanton”

In doing my research, I really did want to go with the OEM+ look that was shown in the reddit thread. There are links in that thread to that head unit that was used. The issue is, none of those head units that don’t connect to a single or double din box have true 5.1 sound. They are all 2.1, and you have to connect them with a RCA cable splitter, which wouldn’t give the output I wanted. These are the parts I ended up going with:

Head Unit
Steering wheel control interface and wiring adapter with 6-pin DIN
Scosche face plate adapter
WAGO wire connectors (you don’t necessarily need these fancy ones, but I like them and that they’re reusable.)

OK, now the steps I took below. I didn’t take any pictures, but the main stereo replacement thread has them so I felt it was a little redundant. There is a photo of the new unit completely installed at the bottom of this post though.

Removal:

1. Disconnect your battery. Seriously, do it. You’ll be removing the climate control unit and this will prevent SRS errors and needing to use VIDA.
2. Pull up on the lip behind the shifter trim where the cupholders are to release the shifter trim.
3. Key in position 2, and shift the shifter to drive to get the trim out of the way. Leave the key in position 2 for later.
4. Remove the 2 T25 screws at the bottom of the climate control unit, behind where the shifter trim was. BE CAREFUL WITH THESE OR THEY WILL DROP INTO THE SHIFTER AREA. Ask me how I know.
5. Pull out and away on the Head unit. Finagle it so you have access to all the connectors on the rear.
6. Remove all connectors. The ones for the stereo are pretty easy, the CCU has a release tab that is tucked out of the way, I used a pick tool to release that one.
7. Remove the 3 T25 screws along the top backside of the silver trim, and release all the clips to remove the trim.
8. Remove the 4 T25 screws holding the CCU onto the housing. Remove the CCU and set it aside.
9. Wiggle the OEM stereo out of its housing
10. Remove the cubby or cupholder if you have it. This will require some gentle prying with a small flat head screwdriver or pick tool.

At this point, I paused to clean the stereo/CCU and CCU itself with a microfiber soaked in some hot soapy water. The previous owner had clearly spilled some sort of soda or coffee into the unit and I wanted to have a fresh start. Moving on!

Installation:

1. You’re only doing parallel connections on 4 connections, so go ahead and connect those between the aftermarket head unit harness and the Crux Adapter harness. Those 3 will be Ground (black), Constant power (yellow), Accessory power (red), and Illumination (orange).
2. Go into the aftermarket head unit harness and separate the wires for Front right(+) and Front Left(-). Connect a wire connector to them to prep. We will be using these later.
3. Connect the RCA connections for front right, front left, rear right, and rear left from the 6-pin din adapter to the RCA harness provided with the aftermarket head unit
4. Connect power antenna (blue wire) from the aftermarket harness to the crux adapter harness AND the 6 Pin DIN adapter harness. This is where the WAGO connectors come in handy, doing a 3 wire splice.
5. Install the 3.5mm SWC wire from the Crux harness into the 3.5mm plug supplied with the aftermarket head unit.
6. Set the jumpers according to the Crux manual on the interface box. OFF ON OFF was what worked for me.
7. Install the Scosche adapter into the center console frame.
8. Install the head unit into the scosche adapter and use the provided screws to mount it to the bracket
9. Install trim pieces
10. Reinstall Climate control unit with the 4 T25 Torx screws
11. Reinstall silver surround trim by snapping all the tabs back in and then securing with the 3 torx screws at the top
12. Bring the reassembled unit back to the car
13. Look at the factory green plug on the factory wiring harness. In pins 10 and 11, there should be a grey wire and a grey wire with a red line. Clip those two wires, leaving enough so you can reconnect later if you desire. Post #48 by “Shredder” on the main stereo replacement thread shows what that looks like.
14. Connect the grey/red wire coming from the harness (not the connector) to the Front right (+) wire from the aftermarket head unit harness
15. Repeat for the grey wire to the Front Left (-) from the aftermarket harness. This is called bridging channels. I’m not exactly sure how it works, I am sure an electrical engineer could tell me, but it does.
16. Reconnect all the factory harnesses. Green main connector for stereo, 6 pin DIN connector, CCU green connector, and the cigarette lighter power.
17. DON’T INSTALL YET. This is your time to test. Reconnect the battery, keeping the key in position 2. At this point the system should power on.
18. Go through your audio, making sure all your speakers work. Program your steering wheel control buttons (there is a field to do this in the system settings of the head unit) and make sure you have volume and track skips working, and you arent getting any buzz or hiss from the speakers.
19. Stuff as much of the excess wiring and the steering wheel interface box into the back of the housing. There isn’t a ton of room back there, so you want to make sure you have as much as possible.
20. Maneuver the unit back into place. Secure the two bottom T25 screws.
21. Reinstall the shifter trim, and shift the car back into park.
22. Enjoy your new carplay/Android auto equipped head unit with center channel!

See below of a picture of the final product. Overall, I am very happy with it. I do lose parking assist, but frankly, I wasn’t using it much anyway since I have a hitch bike rack in the back of the car and it would scream at me any time I put the car in reverse. Keep in mind the perspective in the photo is a little bit skewed, in real life the unit doesn’t block the vents at all.