It is the orange wire. If you have a 71-72, maybe a 70, maybe even other years, the plug at the end of the orange wire plugs into a solenoid looking thing in between the firewall and pass. side inner wheel well...tight squeeze, I've never actually seen what I pulled that orange wire out of...I have to change my heater core in my 72 and heard nothing but headache-type stuff about that job. So I just bypassed my heater core, heat's overrated anyways.