TM 10-6640-238-13 5-57/(5-58 blank) CAUTION Mod Lab ECU opening must be covered to prevent dirt, dust or moisture from entering laboratory, unless replacement is to be immediately installed. 4. Cover Mod Lab ECU opening. a. Cover ECU opening with plastic or suitable covering. INSTALL 1. Remove Mod Lab ECU covering. a. Remove ECU opening covering and clean area. 2. Install Flexible Duct.  See Figure 5-21. a. Install flexible duct (14) on Mod Lab and secure with four bolts (17). 3.     Install Environmental Control Unit (ECU). WARNING Serious  injury  to  personnel  or  damage  to  equipment  may  occur  unless  two  or more personnel are used to install air conditioner because of weight and balance of the ECU. a. Carefully position ECU (2) onto ECU mounting platform. b. Install flexible duct (14) to ECU (2) and secure with 12 screws (11), lockwashers (12), and washers (13). c. Slide ECU (2) into position and secure to with four bolts (8), washers (9) and eight isolation mounts (10). d. Lower upper hold down bar (16). e. Install cable and secure with quick release pin (15) to secure ECU (2) in position. f. Install nipple (7), elbow (6), and fittings (4 and 5). g. Install drain line (3) and connect to adapter (4). h. Connect the two ECU input power cables (1). 4. Apply Electrical Power a. Position Power Panel No. 2 circuit breakers A15CB1, A15CB2, A15CB3, or A15CB4 to ON. b. Position ECU remote control mode switch to operational position and verify ECU operation.  (See Figure 4-15).