No Power to Head Unit

[Gabber-Baby]

Ok, so im getting one of those Thatcham alarm and immobilisers installed in my golf on monday so i can finally start adding all my audio equpiment.

I was brought a Sony Xplod Head Unit for christmas (nothing special but it'll do me for now), my friend tried to fit it a couple of weeks ago and we had no luck. When i brought my golf last November, it didnt have a head unit in it, just a load of wires which looked a bit sorry for themselves. I dont know a great deal about audio but my mate who did that sort of stuff for a living said that all the wires that should be there are there and there's no reason why the head unit shouldnt work. Some of the wires look a bit shredded and all we managed to get from the head unit was a very faint whirring sound, like it was trying to eject a cd but there wasnt enough power.

We looked in the engine bay and there's wire loose on pipes! Whoever had my car originally completely bodged it up. Im wondering if all we need to do is cut back a few wires and reconnect them or whether there's a wire damaged further down the line, or whether there's a fault with the head unit itself? Im going to borrow someones head unit and see if it'll work in my car so we can see if thats the problem.

I dont know if its easier just to get a whole new load of wires and start from scratch. Its just really pi**ed me off because I still need to wire up my subs and my amp and we're having problems just installing a poxy head unit 

Any suggestions?

[S11EPS]

Not being funny or anything, but your buddy who does this for a living should be able to tell you in less than 2 minutes what the problem is - surely he has and knows how to use a multi-meter, which would allow him to identify the wires and determine if you were getting power etc?

It's very difficult to give advice on how to solve wiring issues, simply becuase the person giving the advice doesn't have all the facts to hand. If you're keen to learn and do it yourself get down to your local B&Q (or similar) and buy a cheap multimeter - this will allow you to check voltages and continuity of wires etc.

From your findings there you can determine if you need to run any new wires; I would definutely do this before you think about connecting anyone elses headunit up - you know the wiring isn't all it should be, so identify them and tidy them up first. This will also erradicate the possibility of damaging this head unit you are about to try!!

I doubt your speaker wires (although chopped from the ISO) will be lost/missing, so worst case scenario is you'll need to run a new power cable. This in itself is no bad thing, because at least you'll have the opportunity to ensure you Live Feed is capable of supplying the necessary power to your headunit - bare in mind, when your car was built it was done so with a 4x25watt headunit in mind, and I'm willing to bet your explod unit is at least 4x40watt or maybe even 4x50watt. A decent Live feed will ensure your headunit power demands are properly fed.

If your wiring is in state the first thing I'd do would be to tidy them all up, identify them and wire them into a connector block.
That way, you know exactly where you;re starting from and what should work.

If you need some help in using a multimeter I'll gladly give you some pointers - it's very, very simple for car audio stuff...

[Gabber-Baby]

Thanks for that

Yeah i dont really think my mate has alot of experience, although he did it for a living, he's only a bit older than me so there's probably still alot he doesnt know himself.

Its also trying to find someone who has the time to help me, I have already phoned Halfords and they wont look at it for me unless I brought the head unit from them.

Ive never even heard of a multimeter! 

[S11EPS]

ok, online they only show two models, the cheapest of which is http://www.diy.com/diy/jsp/bq/nav/nav.jsp?action=detail&fh_secondid=9288723&fh_view_size=6&fh_location=%2f%2fcatalog01%2fen_GB&fh_search=multimeter&fh_eds=%c3%9f&fh_refview=search&ts=1203439617427&isSearch=true

If you have a look instore you'll probably find one for around £15.

You use the multimeter to identify which wires do what. It's all very well a Haynes manual telling you what they should do, but until you test them, you just don't know...and it sounds like the wiring in your car has been well butchered, so I wouldn't skip this.

The way in which I'd do it would be to first use the continuity function of the MM to find your earth; Attach one of your multimeter pins to a known good earth (some bare metal in the car) and work your way through the wires in the dash until you hear the MM confirm you have continuity. That confirms you have a good earth connection at the stereo.

Next, switch the MM round to the voltage section as you now want to find your permanent and switched live supplies.

Using your newly-confirmed earth wire as one contact point, tap each of the other wires in turn, looking for a voltage. You should get a reading of just-sub 12 volts with the engine not running. You should only have one of these and it should give a positive voltage reading with the engine on or off.

This is your permanent live.

Keeping your MM switched to voltage, now twist your ignition key round to the position prior to the engine turning (your dash will light up like a christmas tree with the warning lights etc). Follow exactly the same process as above, you're looking for another positive voltage. When you've found one, switch the ignition off and remove the key. The voltage should drop to zero.

Congratulations, you have now found your switched live!!

These are the three wires which, if all present and correct, will govern the powering up and powering down of your stereo and are most important.

Speaker wires should be colour coded into pairs (light grey, purple, green and white, one of each colour being striped with black to denote negative).

Check your power connections are all and get them in a tidy state into a connector block. Then, knowing they're all good you can offer up any number of headunits for test, knowing that your wiring is good.

Any problems, drop me a line dude. If you were local to me I'd gladly give you a hand, as if you know what you're doing, it really isn't a complex job to do.

[Ruji]

MAPLINS
they do em for a 5er

or stretch out to a 10er n u'l get a half decent one....i did n its lasted me yonks:-)