Car radio wiring

[littlepk]

I bought a 97 ford escort yesterday and it doesnt have a stereo installed. I tried to install my own aftermarket one but the wiring is a bit confusing. The original adaptor has been cut off and now there is just a bunch of wires. I've worked out which 8 wires are the speaker leads but have no idea which is the power, earth leads etc. The wires are not in the familiar colours of red, black, yellow, blue and so on. Can someone give me any advice? Much appreciated, thanks.

[Buenchico]

(2-part post):

Get hold of a multimeter from somewhere. They're �5.99 in any branch of Maplins. Some discount stores sell them for less but, unless you've got no friends, family or work colleagues, you shouldn't have much difficulty in borrowing one ;-)

Switch to multimeter to the lowest DC range above the voltage of the car battery. (Typically, this will be 50VDC). With the ignition key out, touch the black probe against any bare piece of metal on the car's chassis. Touch the red lead against each of the unknown leads in turn. The only one which moves the meter will be the 'permanent positive' (i.e. the one which provides continuous power to keep the radio's memory functions working). Label that lead accordingly.

Now turn the ignition key to the first position and repeat the process. The lead which moves the meter this time will be the 'switched positive' (i.e. the one which provides power to the radio while you're driving but disconnects the radio when you leave the car, to prevent draining the battery). Label the lead.

[Buenchico]

With most set-ups, that should only leave one lead. That should be the earth lead. To check, switch the multimeter to the 'resistance' position and (still with the black lead touching the chassis) touch the red lead against the remaining lead. If the needle moves, there's a continuous circuit and you've got confirmation that the mystery lead is connected to the chassis (and hence to the negative terminal of the car's battery).

If, after identifying the two positive leads, you're still left with two leads, it's possible that there might be one lead feeding directly from the battery, while another is grounded to the chassis. If so, they should both move the needle on the meter. It might not make any difference which is which. (Your radio might only have one connection anyway). If you do want to differentiate between them, simply repeat the resistance test with the negative terminal of the battery disconnected. The lead which moves the needle is 'earth'. The one which doesn't is 'negative'.

If you've not actually worked out which leads go to which speakers, simply place a 1.5V torch battery across the ends of two leads. When you match a pair which go to a particular speaker, you'll hear a 'click' from that speaker each time you put the battery across the leads.

Chris

[littlepk]

Thanks very much Chris. I've got a multimeter at home but have never used it. Will follow your advise. Much appreciated, Simon.