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New Head unit has power but doesn't work


prender
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Hi,

 

Title says it all really! I bought a new head unit to replace the stock unit in an S-reg finesse. I bought an ISO loom (universal for escorts) and connected everything up and the power button on the unit lights up - so I know it's getting power - but the fascia won't turn on and the unit won't accept/reject CDs.

 

Does anyone have any experience with this sort of problem? I've jumped to the obvious conclusion - faulty unit - but thought I'd ask those with more experience.

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You havnt blown the fuse in the car have you? when you plugged it in with the ignition off did the cd player make a whiring noise?

 

Just re read what you said, if the power light comes on it has permanant live but no ignition, a radio needs two power feeds to turn it on so it probably is a fuse

 

HTH

Edited by hicksy
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You havnt blown the fuse in the car have you? when you plugged it in with the ignition off did the cd player make a whiring noise?

 

Just re read what you said, if the power light comes on it has permanant live but no ignition, a radio needs two power feeds to turn it on so it probably is a fuse

 

HTH

 

not nessacerally. my stereo flashes a light when the facia is removed. so has a permanent power feed with out ignition.

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You havnt blown the fuse in the car have you? when you plugged it in with the ignition off did the cd player make a whiring noise?

 

Just re read what you said, if the power light comes on it has permanant live but no ignition, a radio needs two power feeds to turn it on so it probably is a fuse

 

HTH

 

not nessacerally. my stereo flashes a light when the facia is removed. so has a permanent power feed with out ignition.

 

That is what i said, it needs two feeds to power up, but only one to make the power light/security light/eject button light stay on

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You havnt blown the fuse in the car have you? when you plugged it in with the ignition off did the cd player make a whiring noise?

 

Just re read what you said, if the power light comes on it has permanant live but no ignition, a radio needs two power feeds to turn it on so it probably is a fuse

 

HTH

 

not nessacerally. my stereo flashes a light when the facia is removed. so has a permanent power feed with out ignition.

 

That is what i said, it needs two feeds to power up, but only one to make the power light/security light/eject button light stay on

 

what hicksy is trying to explain is that every modern headunit uses 2x 12+ live connections into the unit.....one essentially keeps a permenant 12v feed running into the unit to allow the unit itself to retain enough power to remember the way you have its settings configured and saved radio stations.

 

while the other 12v live is there to power the complete unit in its "on" mode (playing your tunes) and this specific feed is only usually active when the ignition is on.

 

that all said, if your reasonably savvy with wiring and have a multimeter handy you could do with checking the units live feeds to make sure the iso adapter hasnt been wired incorrectly for your headunit (happens more often than you'd expect)

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The fuse is intact.

 

My one reservation was the ISO loom. I assume it's ok; I bought it from a reputable dealer - the brand is Autoleads. The wires on the loom marry up to the equivalents on the new unit (according to the manual) but the wires being fed out from the car itself (hope that makes sense) are simply colour-coded, and I've not been able to find anything online that I can check against, i.e. black wire, green stripe = earth (or whatever it is).

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Mk5 & Mk5b 1990-09-01 > 1994-12-31

Red - Perm live

Yellow - Switched live

Brown - Earth

Brown and White - Alarm

Grey and Yellow - Illumination

Blue - Remote/Power antenna

 

 

Mk6 1995-01-01 > 2002

Orange and Black - Perm live

Yellow and green - Switched live

Black and green - Earth

Black and Orange -Alarm

Orange/black or yellow - Illumination

Blue/White - Remote/power antenna

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  • 2 weeks later...

Hi,

 

I've had another look at this and think I might have discovered the problem. There are six wires on the block coming out of the car:

 

Right to left:

 

thick orange/thin black = Perm live;

thick black/thin green = earth;

thick yellow/thin green = ??switched??;

thick orange/thin black = illumination;

thick black/thin orange = ??alarm??;

thick black/thin green = earth

 

I tested them with a multimeter and think I've worked out which are which but there is no reading coming from the thick yellow/thin green wire which seems like it should be the switched-live (and tallies with Dark's list above). I found this a little confusing as the stock radio worked fine - presumably it doesn't need the switched-live to work.

 

I've checked the fuse under the dash and it's ok (plus interior light/cig lighter etc work fine).

 

I'm a bit stumped as to what the problem could be. I thought it might have something to do with the main fusebox next to the battery, but surely if one of those fuses had gone it would have greater consequences than just the switched-live on the audio?

 

Any advice appreciated

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  • 3 weeks later...

OK, bit of an update,

 

Thanks to someone's very helpful suggestion, I hooked up both wires to the car's permanent live - hey presto, the stereo works! All fuses still intact.

 

The fault then is clearly the "car's" switched live. That's the easy bit out of the way - now, how to fix it.

 

Where is the other end of the switched live?

 

I'm hoping that this will be a relatively easy problem to fix. Presumably, the fault is either at the source end of the wire or it's the wire itself. If it's the wire I'm probably screwed because it doesn't look like it's the sort of thing I could replace myself and would be far too expensive to have done at a garage.

 

Also, does anyone know if the stock radio (3000) is supposed to use the switched live? I've not had any problems with the battery draining (I think) but perhaps I'm driving it regularly enough to keep recharging it.

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Hi

 

I have tried swapping the perm and switched live wires before but this just meant that there was no power to the new stereo at all. I think the new stereo needs both the perm and switched to operate.

 

The stock radio doesn't even need the key in the ignition for it to turn on and off, retain the preset stations etc. so presumably doesn't need the switched live at all - although whether this means that it has slowly been draining the battery, I don't know.

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