I have a lennox hp23 411 hvac went to clean out leaves took the fan off but did not unhook anything else fan fell out of my hands and a black wire came unhooked from the other end. Don't know where it was was hooked up to.. purple and orange are still hooked up.

Black usually goes to the contactor. Wireing diagram should be on the back of the door.

Wich slot 1 3 or 5

I got it, has to connect to a relay for some reason.