New Headunit not powering up

Alan Murias

Registered User
Dec 29, 2018
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Hi All, Recently bought a Audi A4 B7 2008, Decided to replace the Audi concert and bought a Kenwood headunit, I have bought the Audi ISO adaptor and plugged my new headunit but i cannot get it to power up, I have ran the red cable to the fusefox and hooked it up to the break fuse with a dual piggyback 10amp, turned the engine on and it wont power up, I have connected the areal as well as i read somewhere it might get the earth from there but still nothing, i have another 2 old headunit which i have also connected incxase the new one was faulty but they wont power up, tried putting the standard Audi Concert and it comes on so what on earth in going on? ive spent the last few days researching this and im about to give up, I have always changed all my headunits in all my cars and have never encountered this, Hopefully someone can help me.
Yes yellow and Red, I connected the red to the fusebox which should be the switch, The yellow is permanent power (memory) I dont think i need to connect that to the fusebox?
With those two wires correct it should at least power up, from memory there are two wires that need swapping over, usually have bullet connectors for swapping on aftermarket units, yellow wire is in the loom and red on a piggyback fuse.
I think there’s a couple of guides online, might be able to trace the issue using one of those, usually the wires have what they’re for printed on then, lucky for me as I’m colourblind, right pain doing wiring
Ok.. So it was the fuse :( on the headunit. Must have blown at some point, So now all i did is replace the fuse on the headunit, ran the red cable to the fuse and it powered on, however stopped a few hours later so i need to make sure the cable hasn't come loose from the back.

1 issue im having is i can only hear sound from the tweeters and not from the other for speakers (front / rear doors)

also the fuse on the headunit is 15 amp and when i used a dual piggy back on the fuse box i used 30 which is for the jet washers and 10amp in the other slot, Will that cause any issues? the one on the head unit is 15a.