TM 10-3930-659-20 16-12.    HEATER BLOWER MOTOR MAINTENANCE (Con't). 3. Inspect impellers for damaged blades and out-of-round.  Replace if damaged or out-of-round. 4. Inspect heater blower motor shaft for free movement.  Replace heater blower motor if heater blower motor shaft 5. Inspect upper and lower heater blower housings for cracks, breaks, or other damage.  Replace if damaged. does not turn freely. 6. Inspect retainer packings for damage.  Replace if damaged. d. ASSEMBLY 1. Install brush (11), spring (12), and brush cover (13) on heater blower motor (17). 2. Install two retainer packings (10) and clamps (9) on heater blower motor (17). 3. Install two impellers (8) and clamps (7) on heater blower motor (17). 4. Position heater blower motor (17) on lower heater blower housing (16). 5. Install  upper  heater  blower  housing  (14)  on  lower  heater  blower  housing  (16)  with  four  screws  (15)  and  eight compression rings (18). e. INSTALLATION 1. Install heater blower assembly (5) in heater housing (4). 2. Connect connector (6) to left panel wiring harness. 16-41