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Discussion Starter · #1 ·
Terrible newbie error with fitting a new Sony Head Unit!

I have tried replacing the old Pioneer HU with a new Sony HU over the weekend but seem to have lost power to both.

I switched the Red and Yellows over in the loom and plugged in the new Sony HU with the ignition on, heard a bit of a whirr and click and thought all would be well but the unit seemed dead. However it will take in a CD (and Eject).

I get no fascia lights and no display and the CD doesnt seem to spin up or play. No difference is noticed with the engine running, ign off etc.

Having given up I plugged the old HU in and that doesnt work either.

Can anyone give any pointers or is it just a fuse popped?

Thx for any advice. I saw the article on the ISO Loom required for aftermarket HUs - does this apply if Ive switched the Yellow and Red over? My ICE shop said I wouldnt need one?
 

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If you plug the standard VW loom into an aftermarket head unit loom,you are still putting a permanent live up the remote switching wire,which is normally the blue or blue/white one,but I've never known this to blow any fuses,if anything does happen,it may mean it won't swich off at all.No aftermarket head unit that I know of will just plug straight into the Veedub loom either without an adaptor,or cutting wires.
 

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Discussion Starter · #3 ·
Thx Image.

Ive been out to the car tonight with my multmeter and cant find any power getting to the VW connector at all - on any of the pins. Have checked Fuse 42 and OK.

Are there any other fuses associated with the HU? Seems odd that the old HU which was previously fine is now dead (due to no power) so must have blown something somewhere. Anyone know of any tests I can do?
 

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Is anything other than the head unit not working,if not it has to be the fuse,have you checked all of them with the ignition on?
 

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Discussion Starter · #5 ·
Just been out again and double checked the VW connector and all dead with ignition turned on. Everything else is working in the car (as far as I can tell). Have checked fuses 42 and the 2 next to it (with the continuity tester) and all good.

Are there any other fuses which could blow connected to the HU?

Thx in advance.
 

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I don't have a Golf (yet!),so I can't refer to fuse numbers in the owners handbook.Some fuses can sometimes show continuity if checked in situ as they can backfeed through a circuit they're connected through.You need to check for 12volts on both ends of ALL the fuses with a meter set on volts range,or with a power probe,if the fuse is blown,you will see ground on end,and 12 volts on the other end.
 

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Discussion Starter · #7 ·
... and having just re-read your 1st reply noticed that the blue/white Amp switching lead was spare - so I originally used that to power the aerial ISO connector. Could this have caused complications, I though it would just give 12v - enough to power the aerial?
 

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Do you mean you used it to power one of these,if so then no.there is no logical reason it could cause a problem.
 

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Discussion Starter · #9 ·
Yes, I used the Blue/white to power the Aerial adapter above. I checked the fuses by pulling them out and putting probe on both blade ends, pretty conclusive test I thought.

So the hunt goes on for missing power.

Anyone give any other fuse numbers to check other than those already done? Ive searched the hell out of the forum and am at a loss. Anyone fitted a recent Sony HU and not needed an adapter look to fit to the VW loom? I spoke to a mate with a new Lupo who dropped one straight in.
 

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Dunno where it's gone then if all the fuses are ok.Check the first two wires shown below for at least 12 volts,with negative probe of meter to a good chassis ground,and also to the brown loom ground wire as well.

The only other fuses I know of are the big fuse links right on the battery,but I'd imagine if you had taken one of those out,you'd also affect a lot of other things as well.
 

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Discussion Starter · #11 ·
Thanks again Image. Ive been looking at my multimeter and after testing another wiring loom and still not finding any power decided to press a button called Hold on the meter - Hey presto. Jeez I feel such an amateur. Sorry for wasting your time.

Looking at the loom again and surprise surprise I have power on all the lower 4 pins of the VW connector with my Black probe on the Brown wire (pin 7) in the connector. 12.4 volts on 8 and 6, 11v on pin 4, 10v on pin 2. Nothing on the top pins.

This is with the ignition switched on.

Im going to look at the Sony wiring again and see where I need power, might be able to swap the pins about in the Sony connector to suit.
 

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Discussion Starter · #12 ·
Just spent 2 hours swapping pins in the Sony harness and testing to no avail. The Sony connector now looks like your diagram Image. (Previously I thought it was the VW loom connector).

I have switched the red and yellows over and gone over all the diags.

The HU is getting power - it takes a cd in and spits it out if you press eject (with a beep). But nothing plays, spins or lights up. I can only think it must be the HU thats gone pop thanks to my wiring previously (even though the HUs fuse is still intact).

Very frustrating.
 

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The fact that it takes the disc means it must be getting permanent live on the yellow,but no switched live on the red.Can you temporarily connect the red to the yellow so that you know both of them are getting at least 12 volts?
 

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Discussion Starter · #14 ·
Good idea Image - about the only combo i didnt try as I sat in the car with the temp dropping below zero last night. There is provision on the Sony loom to combine both Red and Yellow into the main Yellow as this is a provision for cars with no Accs power. I have brought the HU into work with me today in view of getting it tested at an ICE shop.

Do you think the HU wouldnt work 100% if it wasnt getting the switched live?
 

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As long as you've got ground on the errmmm.... ground wire,and 12 volts on the red & yellow wires it should power up with nothing else connected to it,then if you unplug the red it should beep at you to remind you to take the faceplate with you,you can just use a small scrap piece of wire to put 12 volts up the red.
 

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Discussion Starter · #16 ·
It works. Tried your idea of putting power down the red and yellow from the good live and it all fired up no problem. Did this at 11pm last night (after the England game) so couldnt be arsed messing about anymore and shoved the HU into the dash.

So thanks for your help. I just have to find the switched live now to do a proper job. I havent even checked if the illumination is working with the lights.

Thanks Image. When you getting your Golf then?
 

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If for some reason there is a fault in your cars wiring,you can connect both the yellow and red to permanent live,it just won't go off with the key,you'll have to remember to switch off manually every time.

Thanks Image. When you getting your Golf then?
When I find the RIGHT one! I'm not at all fussy,it can be any Mk.4 as long as it's Jazz blue,3 door,GTi (1800 or 2000)non turbo,aircon,less than 70,000 miles,only one previous owner,and all original.
 
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