Ok, so you're putting a MK4 golf headunit into a MK2 Golf, right?
Car WiringIn that case click the link underneath...
http://www.installdr.com/Harnesses/VW-Wiring.pdfIn this PDF, your car SHOULD comply by the 'Harness Colour Codes 2' section.
The 'Harness Colour Codes 1' section is for cars made MK3 Golf onwards.
So Section 2 should help you out in identifying the wiring in the Car.
Headunit WiringFollowing this image, the relevant points on the headunit that serve each purpose are written out below...
Plug #3Car Radio Battery Constant 12v+ Wire: Plug #3, Pin #7
Car Radio Accessory Switched 12v+ Wire: Plug #3, Pin #4
Car Radio Ground Wire: Plug #3, Pin #8
Car Radio Illumination Wire: Plug #3, Pin #6
Plug #2Left Front Speaker Positive Wire (+): Plug #2, Pin #5
Left Front Speaker Negative Wire (-): Plug #2, Pin #6
Right Front Speaker Positive Wire (+): Plug #2, Pin #3
Right Front Speaker Negative Wire (-): Plug #2, Pin #4
Left Rear Speaker Positive Wire (+): Plug #2, Pin #7
Left Rear Speaker Negative Wire (-): Plug #2, Pin #8
Right Rear Speaker Positive Wire (+): Plug #2, Pin #1
Right Rear Speaker Negative Wire (-): Plug #2, Pin #2
So once you've found the correct wire and matching location, it's just a matter of wiring it up and trying it out.
For example (and to get you started)...
[X] THE WIRE IN YOUR CAR. REFER TO THE PDF FOR WHICH WIRE.
Which matches up to
[Y] THE PLUG ON THE BACK OF THE HEADUNIT. REFER TO DIAGRAM AND PLUG DETAILS.
Which in theory becomes....
[X] Left front speaker negative wire (-) =
BROWN w/
BLUE stripe
Which matches up to
[Y]
Plug #2, Pin #6
It's very unlikely you'll need the following details, but here they are so that you know what the other pins on the plugs do...
Plug #1CD Changer Data In Wire: Plug #1, Pin #13
CD Changer Data Out Wire: Plug #1, Pin #14
CD Changer Clock Wire: Plug #1, Pin #15
CD Changer Constant Battery 12v+ Wire: Plug #1, Pin #16
CD Changer Control Signal Wire: Plug #1, Pin #17
CD Changer Ground Wire: Plug #1, Pin #18
CD Changer Left Line Out Wire: Plug #1, Pin #19
CD Changer Right Line Out Wire: Plug #1, Pin #20
Plug #3Signal for Anti-Theft Alarm System Wire: Plug #3, Pin #1
Data Link Connector (DLC) K-Wire: Plug #3, Pin #3
Battery Supply Constant 12v+ Wire for Anti-Theft System (SAFE): Plug #3,
Pin #5
Hopefully this will help in getting the stereo wired up successfully to your car!