S5 Vert. had a second hand stereo.. replaced the stereo and re did all the wiring.. stereo works the car starts just fine.. BUT
when you turn off the car and take the key out. the stereo Stays on.. that is starting issue
Volt checked the 12v constant( correct voltage in every position of the Key)
Ground does have good strong mounting point with continuity
But the accessory position... here is the issue... in acc. it works just fine.. powers up to 12v as its designed to
But when the key is off and out. the voltage doesnt turn right off. its a very slow drain. Still reads 11v after 20 minutes of bieng off..

i orginally thought it was a Ignition Relay Switch.,...i replace that but it seemed that the stereo would stay on alittle while before turning off.. but the orginial issue has started again.. pulled the stereo out checked voltage ( and all the connections that we crimped tight) and once again the voltage is slowly draing and the stereo stays on until i guess the voltage slowly drains and its turns off.. i usually just turn it off on the screen ( but yea)

with that said, i dont think it is the ignition relay on the column or the stereo...
could it be in the Key tumbler. or could it be the main relay...

i tried looking but i never could find exactly what i was looking for ... how to check voltage or ohm of those relay, or how to check my tumbler?

When i put the key in and move to accessory i do not here a click but when i turn to start. the engine fires right up and no issue there..
Maybe im missing another area to check.. iam i wrong for thinking it could be the main ignition relay under the hood, or could it be the Key tumbler, or maybe another Ingintion relay on the steering coloumn...
any idea?????

 

I think some pictures of the wiring to the stereo might help. Is it still an aftermarket stereo, or a stock one, and are you using an adapter to the stock wiring harness, or is it all spliced? There is a chance that the 12v B+ and ACC are shorted together at some point (even in the stereo). More than likely something is just in the wrong spot or backwards and an easy fix. Another issue could be how your radio is hooked up to the power antenna, and how it handles that.

 

Ill get out and take the dash back apart. and get pictures.
it is still an aftermarket stereo,( one that was in the car when i got it was a over 10 year old double din stereo.. the new stereo is a touch screen) the power harness is a is adapter to the stereo wriring.so plug and play.. did not have problems with that until i put in the new stereo stereo. the last stereo did not use the power antenna and i also had no intention of using the power antenna( since mostly i just use the stereo for the carplay. the previous own did re do the speaker wires and added a old amplifier. but those wires shouldnt be causing the issue.
the wiring adapter does match the power wires for 12v constant and accessorie double checked with the wiring diagram. the issue is that there is still voltage in the acc wire after the key is turned off and key it out. makes me think that whatever is between that point accessory in the tumbler or the main fuse is where there is an open and voltage keeps coming to the stereo..( in my mind the stereo still thinks its on because its getting juice. and since there was no voltage loss its going to stay on

i have double checked all the crimp connectors and they are on on snug and not moving.. the ground is in a good spot secured to bar metal. i keep checking voltage at the plug( oem harness to the stereo adapter harness to plug into stock harness. )

the only other thing i could think about is the two wires have rubbbed the insulation off and are touching. but ill double check for that today.

 

update. i didnt unplug the stereo last night to see if it would drain my battery and yup it did.. ill take apart the center console to once again look at things and ill add some pictures

 

Sounds more likely a short then. The ignition switch would have to be absolutely filthy or have a defect to short like that because it has big chunky contacts, so a wire short is more likely. With the key out, check +12v and ACC with a multimeter for short with your adapter unplugged. That might narrow down your search.

There still could be something goofy going on with your power antenna or aftermarket amp scenario. The power antenna is backwards from how most modern head units control. The power antenna mast actuates by the stock stereo grounding the +12v power antenna wire at the head unit. Most modern aftermarket units have a power antenna control that assumes the antenna needs a +12 supply from the head unit and grounding at the antenna. It could be backfeeding voltage.

On the scosche plug and play stereo adapters, especially ones in recent years, I have noticed that they sometimes either have the wires in the incorrect pinout at the adapter, switching amp and power antenna wires, or are just plain incorrect altogether. Would be worth a double check on the labeling for sanity. You may have it correct, but they might not.

As far as the aftermarket amp scenario, the S5 convertibles came with two stock amplifiers separate from the head unit. One was the amplifier for the door subs, which was connected to the front speaker audio outputs as well as the amp turn on line from the head unit. The convertibles also had a separate amp for the headrest speakers built by panasonic, that took the rear audio speaker feed, but at line level voltage instead of amplified voltage for the rear speakers like the coupe. I don't have any pictures or documentation of the panasonic amp for the headrest speakers, but the door sub amp does plenty well if you restore it. How's the aftermarket amp being used, if you don't mind my asking?

 

Quote.
on the scosche plug and play stereo adapters, especially ones in recent years, I have noticed that they sometimes either have the wires in the incorrect pinout at the adapter, switching amp and power antenna wires, or are just plain incorrect altogether. Would be worth a double check on the labeling for sanity. You may have it correct, but they might not....

==i may plug in the power antenna after i jump the care. again.. but that is good info... i have must of back pinned each voltage for constant and accessory.. using the wiring diagram it does have the constant and acc in the right place. double checked that a few times.. always start with the obvious stuff.
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As far as the aftermarket amp scenario, the S5 convertibles came with two stock amplifiers separate from the head unit. One was the amplifier for the door subs, which was connected to the front speaker audio outputs as well as the amp turn on line from the head unit. The convertibles also had a separate amp for the headrest speakers built by panasonic, that took the rear audio speaker feed, but at line level voltage instead of amplified voltage for the rear speakers like the coupe. I don't have any pictures or documentation of the panasonic amp for the headrest speakers, but the door sub amp does plenty well if you restore it. How's the aftermarket amp being used, if you don't mind my asking?

==The headrest speakers work. nut not very loud or clean. the switch panel by the ebrake for the headrest speakers doesnt work..I.e nothing changes when you hit the buttons or lights up... i dont know it the that panel is connected to them anymore.. the aftermarket amp. is a very old rockford fosgate 2 channel and thats only driving the speakers for left and right side of the car. when i first started this stereo install i traced all the wires grouped them and made sure they were run where they were supposed to be. With other stereos i have installed over the years. the speakers and stereo work fine and for the most part sound clean.
the new stereo was working perfectly for a while. would turn off as soon as i turned off the key.. then it would stay on a bit then turn off.. then stopped turning off..(makes me think short still)
but what got me to go back into the stereo was that it had a high pitched squeel that matched RPM. in my mind that sounds like a ground loop or alternator going bad. i have just recently replaced my water pump and took off the alternator. im positive i didnt over tighten that adjustment bolt. and deflection in the belt seems the same after i put it back on.. i marked it to be sure.

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There still could be something goofy going on with your power antenna or aftermarket amp scenario. The power antenna is backwards from how most modern head units control. The power antenna mast actuates by the stock stereo grounding the +12v power antenna wire at the head unit. Most modern aftermarket units have a power antenna control that assumes the antenna needs a +12 supply from the head unit and grounding at the antenna. It could be backfeeding voltage.

==when i get back into it in .. ill crimp the power antenna. i know it works it, i wired it up and it made the antenna rise and could pick up stations.. but i realized i dont use the radio and the antenna was loud. so i just clipped it back off. one sec fix so not that big of a deal.

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Sounds more likely a short then. The ignition switch would have to be absolutely filthy or have a defect to short like that because it has big chunky contacts, so a wire short is more likely. With the key out, check +12v and ACC with a multimeter for short with your adapter unplugged. That might narrow down your search.

That was my thought. its a 33 yo car and the ingition relay for the column was cheap enough to buy a new replacement one form atkins( i think thats where is got it). but i think you are right about there bieng a short.. i did check the voltage at both sides of the plug ( oem side and the plug and play side) and i get the same readings.. i didnt think about unplugging it and checking... now that i think about it i dont even know if i unplugged the connector and physically look inside to see if there was a short...

I do appreciate the extra knowledge.. i kept working where the fault could be in actual components but i think there is a short in the wiring in the stereo area center console.. ill keep volt checking and looking for a fault... starting with the plug and play connector

 

I have a S4 that this exact thing is happening with it too.

Sometimes turn the key off and everything powers off, and sometimes the radio just stays on. I ended up unplugging the radio for now. First time it happened I ended up pulling the fuse cause I was late an appointment

I have a hardwired dashcam power in the same area, but have noticed that I seem to have the opposite issue with it, it is randomly powering off when the car is running, but I think is related.

 

ok opened it up and check out the connector... this is the OEM wiring harness.. not the plug and play and these were the voltages ..
Here is the OEM plug with notes
https://imgur.com/AfmSQ6A

Constant voltage reading checks out
https://imgur.com/lylPNol

Accessory... car off key out...double checked in half hour later still reading same voltage
https://imgur.com/wDgJvd2

So unless there is another main fuse or relay that could possibly on effect just the stereo area. the idea that there is a short is making more sense.... it worked ok for a while then slowly got worse again i doubt its the main fuse relay or thier would be no power if that went.. so it has to be a broken wire or power antenna? possible the control switch for the headrest speakers?

for what it is worth i also when to the fuse box and pulled the plug for the stereo 10amp fuse.. and checked the votage again at the plug 8.7v were read at the fuse taken out.. i dont think that matters cause that should be fuse for the 12v constant not the accessorie.

I also notice i do hear the loud click when i click the key into acc. (starter click maybe) and then the engine turns right over no hesitation, turn the engine off and and it clicks when i turn the key off . i checked the voltage again for this and still residual voltage...
i dont know if this could be a issue.. the main fuse relay from right next to the clutch master

https://www.ebay.com/itm/12561691746...xoCf1gQAvD_BwE

i looked for ways to test it. or a pin out or something..maybe im just throwing wild ieas out now

 

I am thinking that either something with the amp or the antenna, when it is powered on, it is getting a signal to close, and somehow this is keeping it running. I need to rip apart the dash again myself, have just been too busy.

 

the prob isnto powering on everything like that works just fine.. its the powering off thats the issue.. something is preventing it from just shutting off.. ill look at the amp again. but it all checked out last time..

 

You should be able to take the ignition switch off the steering column and just leave the tumbler attached. Then you could bench test it and see if it is the part giving you issues. It isn't likely the point of failure, but not impossible. Also, with the switch out of circuit, you could see if B+ and ACC are shorted to your radio.