TM 9-2320-209-34-2-3 21-17. HEATER CONTROL BOX ASSEMBLY REMOVAL, REPAIR, REPLACEMENT, AND TEST. TOOL S: No special tools required SUPPLIES : None PERSONNEL: One EQUIPMENT CONDITION: Truck parked, engine off, handbrake set. a. Removal. FRAME 1 1. Unplug electrical lead sockets (1) . Unscrew and unplug electrical connector (2). 2. Take out two screws (3). 3. Slide out control box panel (4). 4. Take out two capscrews with lockwashers (5) and two nuts and washers (6). Take out control box case assembly (7). END OF TASK 21-130