The UH-1 Iroquois (Huey) helicopter does not have an APU (Auxiliary Power Unit).
It should have been obvious to Green, Sasha and Wolf that all they needed to do to keep the missile launcher from being controlled remotely was to take out the camera and antenna on the side of it. With the camera the remote operator wouldn't be able to see anything to aim at, and without the antenna it most likely couldn't receive a remote signal.