TM 10-6640-215-13 Table 4-2.  Troubleshooting- continued MALFUNCTION TEST OR INSPECTION CORRECTIVE ACTION 9. ENVIRONMENTAL CONTROL UNIT FAILS TO OPERATE PROPERLY (POWER AVAILABLE). Troubleshoot in accordance with TM 5-1420-371-14 and if necessary, replace faulty unit.  See paragraph 4-28. 10. PURGE DAMPER (INTAKE, EXHAUST, OR ECU INTAKE) FAILS TO OPERATE  . Step 1. Check that damper operating linkage is not loose or broken. If linkage is loose, reattach linkage. Step 2. Check that electrical power is available to damper motor. If linkage is connected and power available to motor, replace motor.  See paragraphs 4-30, 4-31, 4-33 or 4-35 for specific motor. 11. PURGE DOOR LIMIT SWITCH FAILS TO OPERATE. Step 1. Check for loose electrical connections. Step 2. Check that power is available to switch. If power is available, replace switch.  See paragraph 4-29 or 4-32 for specific switch. 12. AIR COMPRESSOR MOTOR FAILS TO RUN (POWER AVAILABLE TO MOTOR CONTROLLER). Step 1.   Check operation of controller (refer to FO-1). Step 2.   Check operation of air pressure switch. Step 3.   If controller and pressure switch are operating properly, continue to troubleshoot the air compressor in accordance with TM 10-4310-392-13&P. If problem cannot be resolved, replace the air compressor.  See paragraph 4-36. 13. LEAKS IN SYSTEM CAUSE COMPRESSOR TO CYCLE ON AND OFF. Step 1. Check air system piping, tubing, and unions for leaks. If leaks are found, repair or replace the leaking item.  See paragraph 4-36. Step 2. Check for leaking air system valves. Replace faulty valves.  See paragraph 4-36. 4-15