Indicator wires ?

Hi I have an audi a4 3.0 cab. B6 2002. The central locking will not operate from the remote key. I have had it checked by audi who advised me that the convenience ecu is faulty and want £350 for a replacement. As this is the only feature that is not working I purchased an after market Central locking unit for £12. I have managed to install this and now have remote locking. My problem however is I am unable to identify the indicator wires which come from the switch. I have tried with a test light but I am unable to pick up the 12v +ve signal from the switch. Dose anyone have any ideas of wiring colours or would I be better off gaining access to the rear of the hazard switch. Any advice would be greatly appreciated. Thank you in advance pete John.