1986 mk2 polo stereo

Hi, I recently bought a mk2 1986 polo 1.3 cl.I am having trouble wiring up my head unit as the wires are strange colors.I have seperated the wires for the three ( why only three) speakers and have one thick brown (earth?) and two thinner yellow one. I'm reluctant to "have a go" as about 5 years ago i had a mk2 golf, wired (for the first time) a stereo in, few miles down the road the wires started melting and something caught fire.I've spent hours looking for a wiring diagram somany thanks for any help you can offer!

If you're unable to get a harness for this car, checkout www.installdr.com for a possible pinout of the factory harness. Also read the sticky "how to figure out stereo wiring", and test the wires with a meter.My ex once told me I have a perfect face for radio.

thanks mate, just figured it out (after a minor shock)