1986 Coupe - Stereo Wiring Quick Question(s)/ Advice

[fallingat120mph]

So, while cleaning up the wiring and checking things over:


Photos below are of my 86' Coupe and the previous owners wiring for an aftermarket head unit:


Photo 1:



Photo 2:



Photo 3:




Head unit/stereo lines are tied into the wires from the ignition switch to headlight switch as seen above. Both fused 40a and 10a constant and switched wires respectively..


My question is: In the above photos is this the best place to wire the head unit in and are the fuses correct. 10a and 40a don't seem right???


Is there a better constant and switched power source to tie into??? I have searched the threads and seems some run constant/permanent power (fused) directly from the battery???


I have recently developed an issue at startup where 1 time out of 10 the head unit will not come on AND the headlights will not work. Most times if I restart the car they both work fine...



Thanks for any input!

Erik

[wrxnofx]

Makes no sense. Where is the stock radio harness? That should provide both constant power and switched power, as well as ground. There should have been no need to tie into the headlight wiring at all. Ironically, the largest fuse in this car should be 25A. However, by default not all wires for the headlights are fused (which is why most people add in the aftermarket relays for high and low beams). Perhaps that's why they added the fuses.

I'd yank all that crap off, add the proper relays to the headlights, and find the proper radio harness behind the radio unit. Then tap into that if you really want to retain the aftermarket head unit.

[blucille]

without the stock radio wiring, I'd go to the fusebox directly and find some switched and constant feeds that are unused, maybe you don't have a sunroof or heated seats or something.

For constant power, you could go straight to the battery, with a fuse of course.

40amp is way too much, unless you have an outboard amp. Typical 10watt maybe up to 20 if it's a real "high power" radio.

[jrwilson]

Just finished this on my car. There should be both switched and constant power available. Confusingly, the colours are reversed from normal - yellow for switched, red for constant. If the stereo has lighting tied to the headlights, you can easily build a blade adapter to tap into the wire on the ignition switch and therefore not cut or damage any wiring. Ground I just used an existing hole in the dashboard.

I'll never understand these hackjobs. It's not that hard to do it right.

[isby]

I believe that the old Blaupunkts had a wiring option whereby the radio could be connected to the headlight wiring. The idea was that the radio would detect when the headlights were switched on and would automatically dim the lights on the radio’s faceplate. This may explain why the radio wiring was tied in to the lights.

[fallingat120mph]

Thanks everyone for the input so far!

So I will be tearing out the wiring from above and starting from scratch. Few questions from the experts here:



1. Running a direct line (constant) from the head unit to the battery what gauge wire would you recommend??? I'll be adding an inline fuse of course and it seems like 15 or 20a would be the best.

2. Where have some of you tied in for switched power?



** With the head unit I do not have a need to tie in for illumination - so not worried there.

** Speakers I have finally worked around the fader and used new wires to all four speaker areas. 9 volt battery is your friend there



I have never used a direct line to the battery so this is new to me (always had a harness or paid to have the work done) - thus all the questions. I want to do this install myself so appreciate the help.



Erik

[fallingat120mph]

Originally Posted by wrxnofx

Makes no sense. Where is the stock radio harness? That should provide both constant power and switched power, as well as ground. There should have been no need to tie into the headlight wiring at all. Ironically, the largest fuse in this car should be 25A. However, by default not all wires for the headlights are fused (which is why most people add in the aftermarket relays for high and low beams). Perhaps that's why they added the fuses.

I'd yank all that crap off, add the proper relays to the headlights, and find the proper radio harness behind the radio unit. Then tap into that if you really want to retain the aftermarket head unit.

Yanking said crap off Have headlight and dash light relay threads printed out and will be adding those over the next few weeks. Thanks!

Originally Posted by blucille

without the stock radio wiring, I'd go to the fusebox directly and find some switched and constant feeds that are unused, maybe you don't have a sunroof or heated seats or something.

For constant power, you could go straight to the battery, with a fuse of course.

40amp is way too much, unless you have an outboard amp. Typical 10watt maybe up to 20 if it's a real "high power" radio.

Going with 15a fuse most likely straight to the battery. Thanks!

Originally Posted by jrwilson

Just finished this on my car. There should be both switched and constant power available. Confusingly, the colours are reversed from normal - yellow for switched, red for constant. If the stereo has lighting tied to the headlights, you can easily build a blade adapter to tap into the wire on the ignition switch and therefore not cut or damage any wiring. Ground I just used an existing hole in the dashboard.

I'll never understand these hackjobs. It's not that hard to do it right.

I noticed that too - red and yellow are reversed. The lighting on the stereo is tasteful and controlled easiest from the head unit itself - good idea for the future though.

Originally Posted by isby

I believe that the old Blaupunkts had a wiring option whereby the radio could be connected to the headlight wiring. The idea was that the radio would detect when the headlights were switched on and would automatically dim the lights on the radio’s faceplate. This may explain why the radio wiring was tied in to the lights.

Thanks for the information. Much appreciated!




Again, thank you so far...Just replaced the ignition switch (pain in the ass job) and wiring through the door jams for the plungers (even worse pain in the ass job) to the dome lights - which were cut like all other wiring. I now have dome lights and power windows that actually work properly after shutting down the car. Always wondered why my windows worked all the time - now I know. Well, back out to the workshop...


Erik

[blucille]

Originally Posted by fallingat120mph

Thanks everyone for the input so far!



I have never used a direct line to the battery so this is new to me (always had a harness or paid to have the work done) - thus all the questions. I want to do this install myself so appreciate the help.



Erik

My various cars, SC's of various years mostly, have an extra 10mm nut on the battery post with a couple of factory high-draw loads attached right there, it's easy to put a ring terminal on a piece of wire and attach there. I suspect you want 10 or 12 gauge, based on load and length.

[jrwilson]

Also, consider using an open spot on the fuse panel. For example I hooked my subwoofer to the unused headlight squirter spot. Personally I've never cared for inline fuses, it makes for difficult diagnosis down the line.

[Packin4]

You should check out diymobileaudio.com and caraudiofabrication.com (the latter has lots of how-to videos, both offer good advice via search function). The most important thing is sizing the wire to the power requirements of your amp; the fuse protects the wire so that you don't start a fire!

[Hotshot]

I just tee’d off of my orig harness. I use the stock set up plus there’s a fuse in the radio. I retired everything to stock in my car.

I will tap into a vent light for the orange night dim switchable wire.

[FrankM_]

Hey, I did the work last year.

• I did not reuse the standard power wire in the harnass (seemed too small for 10A)
• I used a fuse that had almost no load on it (headlight washers) and ran a new wire (2.5 mm2) to the radio
• I did put in a wire from the headlight switch to the radio, so the radio will auto turn on/off with the 'ACC', since I didn't know the current draw, I put a 10A fuse in but I will measure it (one day) to see what it really draws over this path.
• Put in a wire from the ashtray light (close to radio, 'behind the rheostat') to the radio for the dimming of the display
• I ran a separate thicker wire (4 mm2 I believe) from the positive battery terminal to the Subwoofer. And although the subwoofer has a 15A fuse on it, I was more confident by putting a fuse close to the battery inline.
• I soldered in the 3 ISO connectors

As you can see, I was unsure over which path (the permanent power or the ACC power) the radio draws its power, and which one is just for 'signalling purposes' or perm memory. I probably should measure it one day.

[fallingat120mph]

Found some of the original harness I believe. They were mostly cut and were crammed wayyyy up under the dash. I am not sure what some of the connections are for radio, speakers??? I'll upload some photos with some questions.





These are the wires I found today.




1. yellow and brown

2. black/blue stripe and brown w/connector

3. blue/black stripe and w/brown/connector

4. yellow/red stripe and black








--------------------------------------------------------------------------------------------------------

Here are the two I am not sure of - not using but am curious what they are.







----------------------------------------------------------------------------------------------------------





yellow/red strip and black

Tested for power constant and switched/ACC and got no readings - couldn't find any other posts describing yellow w/ red stripe along side the black wire. Not sure what these wires were used for. Let me know if you've come across this before. I assumed it was for power but wouldn't use anyway - running a direct line to the battery.









-------------------------------------------------------------------------------------------------------------------------------

yellow and brown

Tested the yellow and got a reading with the ignition on (ACC). No reading with ignition off. Brown I assume is ground.

I found one post out of 100 that had the same yellow wire being used for ACC. Found here:

((https://forums.pelicanparts.com/porsche-911-technical-forum/1111943-radio-wiring-help-needed.html))


Question for everyone: Would this wire be fine for my modern stereo as the ACC wire??? Very very conflicting opinions...

I did a primitive dry run and hooked things up and everything worked well. Just concerned about draw on the wire with a modern head unit vs the original equipment.









I will be running a fused wire (15a - debated on 10a) directly from the battery and not quite sure about using the original harness with this new head unit even as an accessory connection.

Would love to get rid of all of this original wiring but will clean up and keep under the dash - learned the hard way long ago not to just cut stuff off to clean up wiring

Finally got a new heat gun and will start working on new wiring...will check in here for new input.

Can't thank you guys enough for the responses already. Probably should have documented this more with photos and images of wiring diagrams. Hopefully this will help others down the road.



Again, thanks guys!
Erik

[Synchro Joe]

You might find some help with you wiring here:
https://www.modifiedlife.com/porsche-radio-stereo-wiring-diagrams/

[fallingat120mph]

Originally Posted by Synchro Joe

You might find some help with you wiring here:
https://www.modifiedlife.com/porsche-radio-stereo-wiring-diagrams/

Saw that a few days ago... Couldn't find anything that matched my wiring. Only the listed thread where the poster/OP had no 'red' wire either. So, I have yellow/red stripe (not listed) and no red wires...looked everywhere I could.


Thanks!
Erik

[fallingat120mph]

Originally Posted by FrankM_

Hey, I did the work last year.

• I did not reuse the standard power wire in the harnass (seemed too small for 10A)
• I used a fuse that had almost no load on it (headlight washers) and ran a new wire (2.5 mm2) to the radio
• I did put in a wire from the headlight switch to the radio, so the radio will auto turn on/off with the 'ACC', since I didn't know the current draw, I put a 10A fuse in but I will measure it (one day) to see what it really draws over this path.
• Put in a wire from the ashtray light (close to radio, 'behind the rheostat') to the radio for the dimming of the display
• I ran a separate thicker wire (4 mm2 I believe) from the positive battery terminal to the Subwoofer. And although the subwoofer has a 15A fuse on it, I was more confident by putting a fuse close to the battery inline.
• I soldered in the 3 ISO connectors

As you can see, I was unsure over which path (the permanent power or the ACC power) the radio draws its power, and which one is just for 'signalling purposes' or perm memory. I probably should measure it one day.

Great stuff! Thanks!
Erik

[Hotshot]

The blue and browns are your lights for your hvac. Get some 1.2v bulbs and stick them in. Test if they have power and they are dimable.

[Hotshot]

The yellow red stripe is the DEF icon light coming from the black wire that goes to cig lighter.

The other 2 need bulbs and power the HVAC lights

[fallingat120mph]

Originally Posted by Hotshot

The yellow red stripe is the DEF icon light coming from the black wire that goes to cig lighter.

The other 2 need bulbs and power the HVAC lights

Originally Posted by Hotshot

The blue and browns are your lights for your hvac. Get some 1.2v bulbs and stick them in. Test if they have power and they are dimable.

Man, that makes sense if that's the case. Sometimes things are right in front of you and you just don't see it. I don't drive much at night (Hill Country Texas...a lot of deer) so I have never noticed dash lights or lack there of in this car.

I'll check tomorrow.

Thanks!

[fallingat120mph]

Originally Posted by Hotshot

The yellow red stripe is the DEF icon light coming from the black wire that goes to cig lighter.

I see three slots for bulbs in a face plate but I of course have two bulb connections at this point - looks like fan light (right), direction light (right) and on the left a place for a bulb which would be defrost. The previous owner also cut the wire to the light on the floor board by the heat levers.