Continuity is all well and good, but if the switch doesn't make enough of a connection to properly pull down the circuits in question, the device won't work. The switch is doing nothing more than connecting two points, exactly as your jumper wire does. If it works with the jumper, but not with the switch, you know where the problem lies.

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Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]