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Wiring up a sub to standard head unit


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I have searched and searched for help and answers on wiring a sub and amp to a Mk3 Octavia with an admundsen headunit. The problem is finding a remote live. Years ago remote lives were blue so easy to wire up. The back of the multimedia plug has hardly any different coloured wires. There’s lots of wires but no blue. How can it be that hard to find a remote live. It’s just a live that turns on with the ignition and doesn’t stay on constantly. Has anyone got any advise, images or help on this matter.

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Does that unit connect using a quadlock/fakra connector? These don't have a remote live wire. The 'ignition on' signal, as well as illumination and other info goes via canbus wires.

 

A different place to find a remote live wire is near the fusebox, there might be one or more fuses that are only powered with ignition on. If so you can run a wire from there.

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There won't be a remote wire for an aftermarket amp.

 

Instead, the factory amp will be turned on via CAN-bus. Not seen any aftermarket amps that support this?

 

You should be able to get an ignition live but obviously that's not quite the same. Not sure if there are any units that can generate a remote wire from high level outputs but if there are, that could be your best plan.

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Just one word of caution - never ever assume the function of a cable by it's colour. True, in the aftermarket work it was common for the remote on to be blue, but that certainly wasn't the case OEM !  (Becker used to use black !!!  I used to **** myself the first time I turned the system on after installing one of their units - :sweat: )

 

Most moderm headunits will work with the ignition off - they switch off by themselves after a set period of time to save draining the battery, so in that case connecting your amp to an 'ignition on' source would be pointless.

 

You either have to:

a: connect the amp up to high level outputs (again most modern amps accommodate this)

b: place an in-line switch where you manually control the amp on/off.

or

c: If you can find the wiring diagram for the quadlock, I would expect there to be a power source going to the antenna. (they normally have their own amplifiers which need to know when the radio / sat nav is on/off.

 

If you have no luck with option c: then things to try:

 

Found this diagram for Octavia 3.  http://www.autogenius.info/skoda-octavia-2016-fuse-box-diagram/

 

You only need +12v for remote on - would have to test the voltages but...

 

You can't turn heated front or rear seats on without the ignition being on so there's a potential source. But fuse 27 is even more intersting - it's for the music amplifier. Again would need to test it but there's a possibility that will only be live when the head unit is on.

 

Pointless using power sockets or USB etc as lots of things can be operated without the ignition being on.

 

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Scot5. There is no switched live to the headunit. The car is canbus, therefore uses data from the ECU to allow it to turn on, not 12v. 

 

The better high level converts use sense to see voltage through the speaker cable then sends 12v down the switched cable to the amp. Otherwise you need to find a switched live in the fuse box or make your own

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This probably will not help with the mk3 and maybe pretty common knowledge anyway.  However, the mk2 fl fuse box can be tapped into on the fuse for the rear wiper and also fuse 19 for towbar electrics, these both seem fine for running my dash cam and amp remote.  I am sure things may have moved on for the mk3 though. 

 

 

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  • 3 weeks later...

When fitting a sub to my sons mk III Fabia I took a feed from the fuse box (I think that was the rear wiper) for the remote, I also used one of these tapped into the speaker output.

 

https://www.ebay.co.uk/itm/HIGH-LEVEL-SPEAKER-TO-LOW-LEVEL-RCA-CONVERTER-2-CHANNEL-CABLE-ADAPTER-CTLOC10/361011092624?hash=item540df01c90:g:13QAAOSw2oJZ1P-I

 

Worked fine :)

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