# Help, new headunit wont turn on.



## riotburn (Nov 20, 2009)

Hi i just installed a new 9887 headunit in my 99 A4 that had the concert stereo. I tried putting the car on accessory, and push the on button but nothing happened. I have the blue/red wire hooked to the + cable and the brown wire to the ground cable on the new headunit. i should get something if those are wrong and the others aren't? Any help would be great. I've got all the new speakers in and would to put the console and my seats back in, just need this sucker to work.


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## dolbytone (Jun 30, 2010)

New head units requre at least three wires for power. +12V, Switched, and Ground. If you only connected two power wires you are missing one of them, I'm going to guess switched. Typically new head units have Yellow, Red, and Black as these three wires. I do not know off hand what colors they would connect to in your vehicle.


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## Oliver (Jun 25, 2007)

12 volt.com might have something drawn - diagram


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## riotburn (Nov 20, 2009)

More info:










I dont know if you can see the numbering but I hooked

1 to the ground for the radio
2 to the battery lead for the radio (in the audi manual it says this is Terminal 30?)
3 to the illumination for the radio
4 to nothing, I realize now...
5 to the Switched power lead for the radio

I'm thinking that the 4, which in the manual is called the continuous power supply, is what should be used for the positive connection. Can anyone tell me if this is whats wrong or what is wrong here? Thanks in advance.


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## jimmy2345 (Jul 12, 2010)

riotburn said:


> More info:
> 
> 
> 
> ...



You shouldn't be, first, worried about the car's wiring. The headunit you purchased has 3 wires that need hooked up. The yellow to constant power, the red to switched power, and the black to ground. Now find those three wires in your car and hook them up respectively.

Illumination is your choice. Won't make a difference in whether the unit powers up or not.

Should work after that.


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## riotburn (Nov 20, 2009)

I do have a multimeter, how do I test the wire that is the positive power supplly, the one that always receiving power.


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## bheng (Nov 12, 2009)

i would go out and buy a light test. i always thought that was easier to use. but basically you stick the key in, dont do turn it or anything. and test the wires. the one thats always on, will be running i believe its called the hot wire. i dont even think you need to key in for figure out the hot wire.


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## rexroadj (Oct 31, 2008)

yellow is constant...and means just that! It will always have juice if you have a battery and it works. Red is ignition, and black is ground as many have already said. Only if its hooked up properly! However these are the colors for the deck (most decks) but you need a wiring diagram for your car or a wire harness so that you can know for sure what color scheme the car is using.... They most likely will not be the same....Yellow from the car might not be constant (might not be any yellow at all) etc....


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## jimmy2345 (Jul 12, 2010)

riotburn said:


> I do have a multimeter, how do I test the wire that is the positive power supplly, the one that always receiving power.


Yes. Constant will be on with the car off, and triggered will come on with the car.


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## riotburn (Nov 20, 2009)

OK thanks, yea German cars are more difficult. 

How do I test the continuous power one, do I just set it ohm and test for continuity or am I looking for some kind of voltage?


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## jimmy2345 (Jul 12, 2010)

set it to dc 200...it should read between 11-13 volts with the car off....that's constant.


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## bheng (Nov 12, 2009)

set to voltage and you should see a constant 12v when your car is off.


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## riotburn (Nov 20, 2009)

thanks guys, ill give it ago in the morning and report back.


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## dolbytone (Jun 30, 2010)

Just wondering... Did you chop the car's factory stereo harness or something? If you got a stereo wiring harness adapter for your stereo installation all of the diagrams and information necessary should have been included.


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## goodstuff (Jan 9, 2008)

You want a dmm NOT a test light. And don't be touching/probing any harnesses wrapped in yellow tape.


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## riotburn (Nov 20, 2009)

dolbytone said:


> Just wondering... Did you chop the car's factory stereo harness or something? If you got a stereo wiring harness adapter for your stereo installation all of the diagrams and information necessary should have been included.


Chopped away.


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## dolbytone (Jun 30, 2010)

That is so dirty...


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## ttocs388 (Jun 25, 2010)

you said you have the red and blue wire hooked up to power. The blue wire is to power your power antenna and should not be hooked up to power.

Finally you are pushing the source button to turn it on right?


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## The Baron Groog (Mar 15, 2010)

99 A4 has no ignition/switched live. 

So either run a switched live from one in your fuse box or join the perm and ign wire on your stereo together and hook straight to the car's perm live.

You'll also likely have amped rear speakers for which you'll need an adaptor to run.


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## The Baron Groog (Mar 15, 2010)

goodstuff said:


> You want a dmm NOT a test light. And don't be touching/probing any harnesses wrapped in yellow tape.


Test light is fine for working out live wires in this situation-car's not CAN so any probing is fine!

If you're finding yellow tape behind your HU you have problems anyway-should be at your airbag, not behind your stereo!


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## tinctorus (Oct 5, 2009)

bheng said:


> i would go out and buy a light test. i always thought that was easier to use. but basically you stick the key in, dont do turn it or anything. and test the wires. the one thats always on, will be running i believe its called the hot wire. i dont even think you need to key in for figure out the hot wire.


DONT use a test light...They are for hacks and WILL deploy an airbag or detroy a sensitive module should you probe the wrong wires, I HAVE seen them deploy airbag's and destroy computers

Thye DO NOT have any place in the newer cars of todays day and age, they were FINE 20 years ago when cars were not so integrated and did not have all of the sensitive electronics that today's car's have in them

He has a multimeter now he just needs to learn how to use it, but your advice to use a test light "because it's easier" should have NEVER been said...ESPECIALLY in an audi


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## ryan s (Dec 19, 2006)

The Baron Groog said:


> Test light is fine for working out live wires in this situation-car's not CAN so any probing is fine!
> 
> If you're finding yellow tape behind your HU you have problems anyway-should be at your airbag, not behind your stereo!


My airbag module is 8" below my headunit and the wires run up both sides behind the unit. Remove it...bam...yellow harnesses.

Only way a test light comes near my car is if it's in a case, powered off. Actually, I don't know of any of my professional techs friends who use one...


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## The Baron Groog (Mar 15, 2010)

ryan s said:


> My airbag module is 8" below my headunit and the wires run up both sides behind the unit. Remove it...bam...yellow harnesses.
> 
> Only way a test light comes near my car is if it's in a case, powered off. Actually, I don't know of any of my professional techs friends who use one...


Dunno what car you have but never found an airbag module in an Audi behind the stereo and see them every other week!

He knows which wires he's cut, so shouldn't be probing everything on the car anyway...


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## kyheng (Jan 31, 2007)

Get a cheapest multimeter you can get, test light won't tell you much most of the time.
If you don't know what is what, is good that you redo the wirings, atleast for your +12V and ground. Sometimes by doing so, you will find something interesting compare to your original power and ground. As for the ignition source, just tap another wire from the +12V and a switch and you are good to go.


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## ryan s (Dec 19, 2006)

The Baron Groog said:


> Dunno what car you have but never found an airbag module in an Audi behind the stereo and see them every other week!
> 
> He knows which wires he's cut, so shouldn't be probing everything on the car anyway...


It's in my sig  My response was written since it seemed that you made a generalization that cars don't have the airbag stuff anywhere but near the steering wheel and passenger dash. If that's not the case, I apologize


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## dolbytone (Jun 30, 2010)

I vote he reinstalls the factory connector and buys a stereo wiring adapter for his vehicle to connect the head unit properly. If he chopped the wires right against the connector then /facepalm.

Here's a lesson for anyone considering doing something like what the OP did. All of this conversation about multimeters and test lights is moot if you do things correctly from the start.


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## riotburn (Nov 20, 2009)

Ok I got the headunit to turn on, the switched power wasn;t right. Now my amp for front and rear speakers doesnt turn on! Need help on that now


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## bheng (Nov 12, 2009)

tinctorus said:


> DONT use a test light...They are for hacks and WILL deploy an airbag or detroy a sensitive module should you probe the wrong wires, I HAVE seen them deploy airbag's and destroy computers
> 
> Thye DO NOT have any place in the newer cars of todays day and age, they were FINE 20 years ago when cars were not so integrated and did not have all of the sensitive electronics that today's car's have in them
> 
> He has a multimeter now he just needs to learn how to use it, but your advice to use a test light "because it's easier" should have NEVER been said...ESPECIALLY in an audi


lol interesting enough, i used it on my mercedes. yes a mercedes, and i used it to find my switched 12v. so to the op, if you find a wiring diagram and know where to probe around, a test light works fine. 

and just so you know, i didnt go testing every wire there in on my car. i know it was 1 of 3 wires to find a switched 12v through a wiring diagram. 

and NO its not an old mercedes. its a 2003 not some 20 yo car. it worked for me and i didnt run into problems. worked on many members that are also on the mercedes forum as well. that is why i recommended it. 

and also to the OP, it is much easier to try to find a wiring diagram of your car. go ask the dealership, they will give you on if you need it. search it on a forum.

and i also second the vote on attaching the stock harness and buying an adapter. mine didnt come with a 12v switched from my adapter so i had to find a 12v switched btw.

so to tinctorus, i am sorry and stand corrected. it worked for me when i did my car audio myself. so i recommended to the OP. i had everything hooked but the 12v switched. on the forum it was recommended to pull it off the cig lighter. and i needed to find which of the 3 would be a 12v. found it, and it didnt deploy any airbags. didnt fry my computer. everything worked out fine for the most part.


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## riotburn (Nov 20, 2009)

I got the headunit working, the switched cable wasn't hooked to the right cable. Fixed it and now it turns on. 

Now the amps wont turn and I dont know why. Yes I put the fuse in the power wire...Help!

The remote and power all check out on the multimeter, cant find the fuse on my 400-4


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## riotburn (Nov 20, 2009)

I tried jumping the connection between the remote and the power and amp still doesnt come on. I did the same thing for subwoofer amp and that one did turn on. Is the amp itself ****ed up then?


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## jtavrisov (Jul 5, 2010)

Triple check the wiring, make sure you get a good contact.
I once thought my amp was broken because it wouldn't turn on and the turn on lead had actually recessed back into it's insulation
and I got no contact.

For the amp I would unplug all the speaker and RCAs and just have the power, ground and remote turn on.

Realize that the turn-on lead will turn the amps on only if the HU is on. Be careful with the turn-on, sending too much power by accidentally touching the wrong wires will destroy the HU. It's nice to fuse that wire but I never got around to it.


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## Austin (Mar 12, 2009)

dolbytone said:


> I vote he reinstalls the factory connector and buys a stereo wiring adapter for his vehicle to connect the head unit properly. If he chopped the wires right against the connector then /facepalm.
> 
> Here's a lesson for anyone considering doing something like what the OP did. All of this conversation about multimeters and test lights is moot if you do things correctly from the start.


Really? You think everyone should use a wiring harness? There is nothing wrong with lopping the old connector off and connecting the wires directly. It's what i did and many other members here have done.


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## jtavrisov (Jul 5, 2010)

Whats wrong with using a harness. Simplifies the procedure and makes removing and replacing much easier.

I see no negatives in using a harness and a couple without.


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## riotburn (Nov 20, 2009)

Less arguing about harnesses more helping me and my amp problem.

I tried jumping the remote turn on to the power and it didn't work. I tested all the connections and they're all receiving the proper power. I bought this amp used, the other amp I bought from the same person turns on no problem. I'm starting to think its the amp and not the wiring. I dont believe this amp has an internal fuse either to check for.


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## dolbytone (Jun 30, 2010)

Austin said:


> Really? You think everyone should use a wiring harness? There is nothing wrong with lopping the old connector off and connecting the wires directly. It's what i did and many other members here have done.


I absolutely believe that chopping factory connectors is like making a permanent modification for the sake of installing temporary equipment. It's problematic and I see no up side.

Now for addressing the amplifier situation. The fact that you have two amplifiers enables you to use wiring going to the _known good_ amplifier to see if the questionable amplifier is bad by simply swapping some things around.


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## riotburn (Nov 20, 2009)

dolbytone said:


> Now for addressing the amplifier situation. The fact that you have two amplifiers enables you to use wiring going to the _known good_ amplifier to see if the questionable amplifier is bad by simply swapping some things around.


I just tried doing that but no luck. I did some more testing with the multimeter, but I dont now if it means anything...Using Vdc50, I had one lead touched to the screw that holds down the ground wire on the amp, then touched the other to the screw that holds down the constant power on the amp and only got about 8volts. Then touching the positive lead to the remote wire I maybe got a 1-2 volts, mind you I still had the remote jumped to the power wire. 

Then I touched the ground lead to metal surface on the car, and touched each screw down on the amp (power, ground, and remote) with the positive lead and each one gave 12-14volts. 

Does that mean anything in terms of solving my problem? Also to give more background about the setup, the 4 gauge power wire is coming from the battery to a distribution block that splits it into 2 4gauge wires. The remote wire is coming from the headunit and I have a wire tapped to it to split the remote for the second amp.


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## dolbytone (Jun 30, 2010)

> Then I touched the ground lead to metal surface on the car, and touched each screw down on the amp (power, ground, and remote) with the positive lead and *each one gave 12-14volts*


You should not be getting 12VDC by metering between a ground wire and a ground.

Using _good_ wiring known to turn on your _known good amplifier_ and getting no results on the questionable amplifier points towards an amplifier problem... i.e. you probably have an amplifier that needs repair.

This is assuming a few things like, you transferred the +12VDC, Switch, and Ground from the good amp and still was unable to turn on the questionable amplifier. If you did do this, I say bad amp. If you did not do this, you should give it a try so you can narrow down where your problem lies. If you are using two different grounds for instance, it is possible one is not sufficiently grounded and the other amplifier is.

No matter how many times or how you use your multimeter to try and chase down the issue, the fact that you are having so many questions about voltage leads me to believe you do not have adequate understanding of circuitry for any results you get to be meaningful to you. This is why I suggest you start swapping things to find where the issue lies.


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## Austin (Mar 12, 2009)

dolbytone said:


> I absolutely believe that chopping factory connectors is like making a permanent modification for the sake of installing temporary equipment. It's problematic and I see no up side.


In some situations yes harnesses are good if you plan on selling the vehicle and putting the stock head unit back in, but my car is old enough to where an aftermarket one is better. It's a 94.

You were referring to cutting the factory harness off to be something bad like walking into a church and yelling "the devil has arrived!". That is why i responded saying it wasn't bad and that harnesses aren't bad either.


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## riotburn (Nov 20, 2009)

dolbytone said:


> You should not be getting 12VDC by metering between a ground wire and a ground.
> 
> Using _good_ wiring known to turn on your _known good amplifier_ and getting no results on the questionable amplifier points towards an amplifier problem... i.e. you probably have an amplifier that needs repair.
> 
> ...



I just understand a lil and that I should be getting 12-14 volts for power and remote wires. Its a mouthful to articulate about what happened. But i did swap the wires from the good amp and that still didn't work. 

To say it better, the voltage I was getting for power and remote when using the screw that holds down the ground wire was less then 12 volts. When I touched the ground to a point on the car I was getting 12-14volts. This was using V DC 50 on the mm.


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## riotburn (Nov 20, 2009)

Got the amp working, I put the ground ring terminal on better. Weird that it had worked for the other amp. But now I got great sound and I haven't even tweaked it yet. Next is building a fiberglass sub box....

Thanks for all your help!


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