so when i bought my z...it had this installed..the owner said the heater core went and this were a temp fx.. that was 15 years ago and he has since forgotten..so now i have this danglin from my interior off to the side...my fan does work and turn on but i dont know where to start to get these guts back in the right spot..here is a pic.

 

looks like he rerouted the heater control valve... my guess is the heater core is fine but the valve went out and instead of replacing it he just rerouted the it and put in a manual valve..

heres an older post
https://www.zdriver.com/forums/280zx-performance-technical-79/heater-problems-22982/