'78 280Z Dash Wiring

According to the mechanic that I have working on my air conditioner, some of the wiring in the dash is "bleeding" over to other components and could cause the battery to go down when the vehicle parked for several days.

Would anyone know if I have to replace the Harness Assembly that controls the wipers, rear defroster, air conditioner, etc. or if there are portions of it that can be replaced? Also, is there anywhere that I can find replacement wiring that did not come out of another car that has been sitting in a junkyard for several years?

Be gentle...I am a new member and haven't owned a Zcar in 26 years.

Hornz