Stevenwr

Hello, last fall I bought my first 928 an 88 S4. Over the winter I've been working on it: recovering dash/pod etc. A PO removed the original stereo and amplifier and installed a Pioneer DEH-245 with no amp. I bought a Kenwood KDC-X500 and Alpine KTP-445U amp. I have a lot of mechanical experience but have never dealt with stereo wiring and need some help. It seems the PO piggybacked the pioneer harness to the stock harness. They wired the constant power to terminal 5 (throttle) and ACC wire to terminal 2 (suppressor). The constant power wire has an inline fuse (10A) and a black box that I opened up and have no idea what it is. The Kenwood wiring instructions show red wire to ACC and yellow to constant power. Should I also piggyback to the old harness or just cut the old harness out all together? Should I also use the pioneer fuse and black box on the Kenwood constant power connection?

Thanks.

Captain_Slow

Steven,
My situation was different because I was working with a system using an external amp, but the pictures below might help with your head unit connections. The thing in your hand looks like a transformer coil. I can't imagine what it is for. Those are common inside a Power Supply. Maybe it's a noise suppressor, but often these things can actually make noise. They buzz...whine...that's why it has the green tape wrapped around it. Likely there's tightly wound copper wire under the tape.

The Sony head unit in my car was also spliced into the OEM harness. I wanted to keep the original harness in case someone ever wanted to restore the car to original...not likely, but I didn't want to wreck the opportunity. So I observed the connections while reading the connection instructions for my new Alpine.

One of the best and simplest ways to avoid electrical noise (from alternator or electric fan motors) making it's way into the system (heard through the speakers) is to have very good grounds. So don't rely on the black to brown wire ground connection. I added a ground wire from the head unit chassis to a good ground point on the torque tube tunnel nearby under the console.

So here are some pictures that may help you. Notice the fat yellow battery wire from the new Alpine harness goes to the thin red wire on the OEM harness and the thinner red ignition wire from the Alpine harness goes to the thicker red wire on the OEM harness. Black ground wire from the Alpine harness to brown ground ("Earth"...kinda makes sense to make it brown) of the OEM harness. I have no gizmos in my wiring...clean sound.

Hope these pics help. I reused the piggybacked connections to the OEM harness to avoid molesting it any further.

Stevenwr

Thanks you that helps a lot. I noticed you didn't put inline fuses to your power wires, not necessary? The stock 928 antenna connection has a small black wire going to pin 4 (looped white wires) of the stock connection, what is it for?

Alan

Remove all the added wires and connect your new harness to the factory wiring. Remove the old speaker connectors at the sill area where the amp was - that is a mess.

The black box is a suppressor/inductor for noise reduction. You already have (better) suppressors installed on the constant & switched supply ('Suppressor' & 'Throttle' are in this case basically the same thing one just has an added spike suppressing diode).

Alan

jwyatt8171

For what it's worth in the past I have always ran the ground wire from the head unit to the amp. Then ground the amp and head unit to the same location. Don't ground the head unit to the brown wire behind the radio only ground it where the amp is grounded.
Any other audio components should be grounded at the same point as well.

Captain_Slow

I didn't put any in because none were there or prescribed by the instructions. Do whatever Allen says to do

Wisconsin Joe

The small black wire running along the antenna coax is the antenna amp.
It takes 12v. I used the 'power antenna' lead from my head unit to power it.

The windshield antenna is virtually useless without it.

I really can't make heads or tails from your pics, but the wiring is fairly straightforward. Get a copy of the WSM - there's a link to a free download in the "New Visitor" sticky.
It has wiring diagrams, so you can find the appropriate details for your year.

In my 85, red was constant power (came from the interior light circuit). Red with white stripe was switched power (came from ignition switch). Blue/black stripe was lighting. Brown is ground. Brown is always ground.
Check the wiring diagrams to make sure about your car. The wiring varies quite a bit from year to year.

Alan

Stick with the stock wiring - it already grounds at a single point "MP V" (Ground Point 5). Constant power comes from Fuse 22 via the stock suppressor, Switched power comes direct from the ignition switch via the stock suppressor - don't change any of this.

Alan

Stevenwr

You guys are gold...thanks for the info. The head is wired in and now onto the amp.

Alan

Good !