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Pete, Technician
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Experience:  17 years automotive training and experience.
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Audi A6: I just installed a new headunit for my 98 A6 2.4.When

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I just installed a new headunit for my 98 A6 2.4.
When volume is at about medium, the speakers cut out at basshits.
Stopping the music caused a buzzing sound, then leading to headunit powering off.
It will then start flashing, as if trying to power on.
Turning off and on ignition powers the HU back up. But audioproblem persists.

Any ideas?
My name is XXXXX XXXXX I am a professional here at Just Answer. I noticed that your question was not getting a response and thought I would see if you still need help with this.I apologize for the delay and I hope I can still assist you with this here.

Was this an issue with the old and newly installed head unit or only with the new installed head unit?

Was the head unit you installed the correct factory head unit for this vehicle?

Let me know so we can continue,thanks Pete
Customer: replied 4 years ago.

The isssue occured only with the new headunit.

Both are aftermarket headunits.


Old one was a Grundig SCD 5690 (4x25w)

New one is a Pioneer deh-4500BT (4x50w).


Today, i switched the yellow/red cables again.

The HU now had full power. But after a few hours it shut down for 20 seconds, randomly.


Now, (5 minutes ago) the head unit will not turn on with the switched red/yellow.

Is this red/yellow the constant voltage and ignition voltage signals to the radio that you are switching?
Customer: replied 4 years ago.

That is correct.

Somehow, the Red/red, yellow/yellow doesnt power enough; creating voltage drops.

WHEN the red/yellow combo works, no voltagedrop, thus... it does not always stay powered.

Have you tested both of these wires to see if one is receiving battery voltage at all times and the other is when the key is on and that neither of them drop voltage or is one found dropping off in voltage?

Let me know,thanks.
Customer: replied 4 years ago.

Checked this now.

Yellow @ 12v constant

Red @ 5-6v by ignition.


Any way to fix the low voltage by ignition?

Do you have any other wires at the radio that provide 12 volts with the key on?If so this is the wire I would use if it isn't tied into anything else here.It may be possible you are using the wrong wire for ignition voltage to the radio or there may be a fault with the fuse for the radio loose in its socket or damaged terminals or wiring at the fuse box or a possible electronic ignition switch fault.Usually if this is an ignition switch fault though it would cause other electrical issues.

I would check and see if there is another wire for the radio that has 12 volts to it with the key on and use this one.

Thanks Pete
Pete and 7 other Car Specialists are ready to help you
Customer: replied 4 years ago.

No other sources 12v ignition live by radio.
I noticed some people taps from cig light.
As i am never using the cig light; i could just steal the ignition live from there, cant i?

Is it a difficult task?

I apologize for the delay.

If you do not use the cig lighter and you know for sure it only has voltage with the key on you can tap into this wire for your ignition feed to the radio and use this and the radio should then operate properly from there.Make sure your constant voltage is good as well as your ground and if all o.k. I would try and tap into this wire for ignition voltage.

You would have to test the wiring at the cig lighter to find one that has ignition voltage (12 volts) with the key on and then run a wire to it discretely hiding it under trim etc. up to the radio.Make sure you tape off any exposed wiring at the cig lighter and radio.You can purchase a scotch lock to tap into this cig lighter wire this way you don't need to cut the wiring.

Thanks Pete

I am following up with you to see if you still needed help with your question you had asked.If my help didn't satisfy your question please let me know so we can continue.

Thanks Pete
Customer: replied 4 years ago.



I was out of the country im sorry.

I am currently checking for any free switched live at the fusebox. Maybe pulling new wire.


For cig light; should i tap in by fusebox or remove the center dashboard by the radio?

i dont use ciglight anyway.

Customer: replied 4 years ago.

That being said; do you know which numbers at the fusebox that are switched live?

I apologize for the delay.

Can you tell me the color wires you have in the vehicle harness that are connected to the radio as well as any other bare wire colors not connected but are at the radio itself?

Let me know,thanks Pete
Customer: replied 4 years ago.

Vechile harness has red/blue (constant) brown(ground) and blue/gray( switched).no other wires in harness..


Really confused now.In the manual for the HU it says;

Yellow - Constant

Red - Ignition


So for me it would be;

Yellow -> Red/Blue

Red -> Blue/gray


When connection is:

Yellow -> Red/Blue

Red -> Blue/gray


SOMETIMES i get perfectly good sound, no problem everytime it turns on.But often the HU doesnt power at all (like right now..)


When connection is:

Yellow -> Blue/gray

Red -> Red/blue


The unit turns on everytime. also powers off when lights go off.

Sound differs alot.

Sometimes i can play loud, but most of the time- it voltagedrops,also; I regularily experience the speakers making a buzzing sound (going louder) then HU powering down, not being able to restart until powersource is disconnected (engine off, example)



This seems like a simple issue, but i cannot wrap my head around it, and it is starting to bug me alot. Stereo working "sometimes", just doesn't cut it..


PS. Used the voltagemeter on the ciglight. It too powers from turning the "electrics" on, not only by key-in-ignition.

O.k.,If my diagram info is correct your vehicles radio harness should have a red and blue wire that is the constant power that should connect to the yellow wire to your radio.

Then you should either have a black and red wire or solid red wire that is switches ignition power that connects to the red wire on your radio.

Check and see if you have this ignition wire and if it tests and has ignition voltage on it with the key on and let me know.

Thanks Pete
Customer: replied 4 years ago.

not by my car at the moment.

But i do not recall any red/solid red wire at the harness.

My "switched live" is blue/gray. Although its only 6v..

Can you re check to see if you have a black wire with red stripe or solid red wire and let me know when you can?
Customer: replied 4 years ago.

I will check in a few hours.

O.k.,let me know what you come up with here.
Customer: replied 4 years ago.

There were no that sort in the harness.

Mind i have to connectors; one brown and one black.

The brown connector seems to have all the speakers lined up.

My info shows a different diagram slightly off from your vehicles wiring here.

Can you gain access to the cigar lighter wiring and if so can you test to see which one is hot/has battery voltage with the key on or does it have voltage at all times key on or off?
Customer: replied 4 years ago.

Cig-lighter shows 12V when ignition off/no key, although not lit.

(either that or with lights on.)


I have yet to become able to get to the wiring, i just checked from the ciglighters core.

O.k.,since my diagrams do not match fully with your vehicle here it is difficult to say where you can tap into an ignition source wire to get ignition voltage that comes on (12 volts) with the key on and turns off with the key off.

What needs to be done is to find a good ignition voltage source wire that either isn't being used or has a high enough amperage fuse to handle powering what is powers already as well as adding your radio to it and then tap into it to power your radio with the key on.The best place of course is the electronic ignition switch itself installing a fused wired into it.

I wish I had better diagrams on this here to tell you which wire you can do this with but unfortunately my info isn't matching your vehicle so you will have to have this further checked/tested to locate the voltage wire you can use here.

Thanks Pete
Customer: replied 4 years ago.


I just got into the fusebox (difficult...)
Now i have loads of wires to choose from.
Since i never use the cig-light, i think i'll just tap from it.


Can you mention some 12V sources that i can use?

I'm thinking of using a 10a or 15a fuse.


EDIT: Damnit, my ciglight is a constant. 12V. Not sure why...
Now i really need other options..



I am now concidering pulling a new wire from a switched live to the radio.

Customer: replied 4 years ago.


Just as an update;


I fixed the issue.

I tapped the mirror-heating with a new cable, running directly to the 6V cable. My HU now recieves 12V switched, and 12V constant. Everything runs nicely.


Thank you for your support.

I apologize for the delay.I am glad to hear the problem has been resolved.If you need anything else let me know.

Thanks Pete