79' SC radio schematic?

[Tommy Z]

Good Morning All,
In the search for improved audio in my SC I am turning toward removing the head unit and installing a bluetooth amplifier that will stream music from my phone. Radio delete plate will house the amp control. I'm not well versed in audio electronics and may enlist the help of an expert who posed a concern that our factory speaker set up may have a common ground which could complicate things. I'm wondering if anyone knows and if someone might me able to share a schematic drawing of the factory system? Has anyone gone the route of removing the old Blaupunkt and utilizing some of the existing speaker cables to work with a new bluetooth amp? Any help or info would be appreciated.

Thanks!

[FrankM_]

I don't have the radio schematic of the model 79 lying around, but I did a couple of changes to my system as well ('85).

First of all - for a 400W amplifier - I would not reuse the standard power supply from the harness. In my case it was a 1 mm2 cable and a 5A fuse.
I reused one of the 25A fuses that was not really loaded : the one that supplies the cabrio motors (not present since I have a coupe) and the headlight washer system (hardly use that) and used a 2.5MM2 wire to the head unit (which had an on-board fuse of 10A).

Secondly, for the amplifier (sub in my case) I put in an extra wire (min 4mm2) from the battery with an inline fuse close to the battery.

I understand you are going to delete the radio head unit, so in your case you will only need to run one new power wire to supply the amps for the 400W amplifier.

I did not find an 'ACC' cable present in my car so I ran a small cable from the contact lock under the dash to the radio location. It is just for convenience, now the radio turns on/off with the car. If you don't need that, there is no need to supply the ACC cable.
However, if your Kenwood amplifier needs a 12V remote signal to switch on (typically the blue cable - and typically provided by the head unit), you could use the ACC connection from the contact switch to signal the amp to turn on/off.

For the speakers, all four had a 2-wire cable (so with their own proper ground cable, no worrier there).

So pretty doable DIY job :
- run a separate cable from battery with an inline fuse near the battery to the amp location (Yellow cable on the Kenwood installation manual)
- for remote turn on/off of the amp : run the blue cable from the Kenwood harness to your key contact switch (this will not really deliver amps/power, so you can splice this off any existing ACC wire coming out of the switch)
- run the black wire from the Kenwood to a good ground (I used a sheet metal screw under the passenger floorboard)
- connect the four speaker wires (and their grounds) to the Kenwood
- plug in the remote control

Done

[Tommy Z]

Thanks Frank, that's helpful. Did you re-use your existing speaker wires or run new ones? Also, if running a new main power from the battery to the Kenwood, do you think it's safe to re-use the existing radio power to a USB charging port that I was hoping to add to the radio delete plate?
Thanks again. I'll keep searching for the wiring diagram if anyone has one?

[FrankM_]

Yes I reused the wiring to the speakers but I did not put nearly that amount of power in. I am using the output from my Blaupunkt head unit.

The usb question depends on the power that it will require but 5A at 12V should be more than ample for a USB charger (typically 2A at 5V output, so max 10W, that would roughly translate to max 1 A at 12V)


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