Step that won't drop down

[Bill McNamara]

I have an 1985 345 with a single step that will drop down only when the engine is shut down. It is suppose to drop down when the engine is running and the entry door is opened. It doesn't. It is vacuum operated. There is a wire that drop down to the area behind the step from the door jam switch. There is nothing to connect it to. I think something is missing but haven't a clue as to what it might be. Don't know where to look for help ? Whenever I go to a rally I look for another "85" that I can look under. No luck there..... My friends have an "86" but their step is electric.
Any ideas