Fog closing persons without function V40 Bj.98

Hello everyone. I have a V40 Kombi Bj.98. I am despairing at the fog closeer even though there is good information about it here. But maybe someone has the serious tip for me. The said lamp does not want to funze. I was allowed to try out the light switch from a Volvo V40 Bj. 97 just arrived at the scrap yard, but without success. There is no click, no visible lamp in the display from the tacho and of course no juice arrives at the rear. However, I have an AHK and an ECHTEN ELCH. That means it burns immediately light, as well as I turn on the ignition!!! Now my question has someone the IDEE?? which cable color to the rear light should I look (eventual break?) so that I can exclude the next error? in 4 days I have to present the elk again at the tuv. In advance thanks to the elk father I have a V40 Kombi Bj.98.