As some of you know, we discourage head-unit replacement. Well, we had a client here in Portland who wanted a Level Two audio upgrade and also wanted navigation - so we ordered the needed parts for the new head unit and the head-unit retention as well. When the car arrived, it turned out to have factory front and rear PDC parking sensors. I didn't even KNOW that you could get front parking sensors in a 328, but I do now.
The customer wanted to keep the front and rear parking sensor alerts (we were installing a backup camera too, but there you go, no one wants to lose a feature). So here's what we did:
- We knew we wanted to retain the stock deck somewhere for software-update reasons
- The factory system was Stereo, which meant the chimes and the PDC alerts all came out of the stock speakers from the head unit
We took a BMW rear speaker takeout which a client had left behind (we always give the takeouts back, but some folks don't want them) and we installed it under the dash panel in the center channel location. We assumed we would need the grille, but it turns out that for chime and alert use, it's plenty loud just though the stock trimpiece.
We drove the speaker off of the L+ and R- wires of the front output channels of the Professional CD Player deck. This gave us PDC alerts off of either the L or R channels from the same speaker.
We then installed HiFi tweeters under the rear deck grilles, without the tweeter capacitors. These tweeters are connected to the rear speaker output channels of the Professional CD player, and play the Rear PDC alert. The stock rear speakers are connected to the new system. This works great - we keep all chimes, we keep rear directional PDC alerts, and we keep front PDC alerts (we lose the L/R directionality with the PDC though).
We also used the BMW AUX jack in the console for the Alpine AUX inputs, and used a flush-mount USB extension for the USB port on the back of the Alpine to put it in the same console pocket as the AUX.
The head unit is under the trunk floor wit the faceplate removed. It remains on the MOST and CAN networks, but is muted as far as audio goes.
The switch relocation part is done for some reason in a completely different sheen and color and texture than the dash bezel. Tom matched the color to get it to look like this.
Finally, here are some pics of the deck:
If we were doing a head unit replacement in a Premium Sound car, I don't know how we would retain PDC or chimes without recoding. I'm pretty sure this is the best approach for chime retention, so I'm going to recommend recoding for any of these that require chime retention or PDC retention in the future. If you only have Rear PDC and you do this, it's easier to add a backup camera, seriously.