AV FANS FAIL
(Advisory)

The three conditions that follow occur:

1. The aircraft is Weight OFF Wheels
2. The left air-conditioning system controller (ACSC) senses that the avionics rack supply fan does not operate correctly.
3. The right ACSC senses that the avionics exhaust fan or the avionics exhaust-fan converter does not operate correctly.

• Avionics Rack Supply Fan (B67)
• Secondary Power Distribution Assembly (SPDA) 4 (A16)
• Air Conditioning System Controller (ACSC) 1 (A87)
• Avionics Exhaust Fan (B62)
• Avionics Exhaust Fan Converter (B29)
• AC Power Center (ACPC) (A54)
• Air Conditioning System Controller (ACSC) 2 (A88)
• Associated Wiring

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

For Avionic Rack Fan

1. Swap ACSCs.
2. Make sure power is present at the Avionics Rack Supply Fan.

   1. If power is present, go to step 5.
   2. If fault remains, continue with next step.

3. Perform wiring checks between SPDA4 and Avionics Rack Supply Fan.
4. Replace SPDA4.

   1. If system checks are good, do close out.
   2. If fault remains, continue with next step.

NOTE 1: If SPDA 3 has been swapped with SPDA 4 a fault may have been transferred to another system on SPDA 2 ref Build 4 load lists with Pinout.xls (Available from FSR).
NOTE 2: When swapping SPDAs, it is possible to loose your DC cabin feeds. Check the EMS-CDU Switch Control Page 3 under SYSTEM - CNTL button. First page is AC feeds 2nd and 3rd are DC feeds that will toggle off.

5. Perform wiring checks for the wires between Avionics Rack Supply Fan and ACSC1.

   1. If system checks are good, do close out.
   2. If fault remains, continue with next step.

6. Replace Avionics Rack Supply Fan.

   1. If system checks are good, do close out.
   2. If fault remains, continue with next step.

7. Perform wiring checks between JB5 and DAU3.

   1. If system checks are good, do close out.
   2. If fault remains, continue with next step.

8. Swap DAU3.
9. Do close out.

For Avionics Exhaust Fan

1. Check that the circuit breaker for the avionics fan is 'IN' on the EMSCDU AIRCOND/PRESS page 1.
2. Make sure there is not obstruction in the avionics Exhaust fan. Make sure the avionics Exhaust fan is not making any abnormal noise that would indicate an avionics Exhaust fan deficiency. Remove FOD as required.

   1. If system checks are good, do close out.
   2. If fault remains, continue with next step.

3. Perform wiring checks between ACSC2 and avionics Exhaust fan converter including the ground.

   1. If system checks are good, do close out.
   2. If fault remains, continue with next step.

4. Perform wiring checks between avionics Exhaust fan converter and avionics Exhaust fan including the ground.

   1. If system checks are good, do close out.
   2. If fault remains, continue with next step.

5. Perform wiring checks between avionics Exhaust fan converter and ACPC.

   1. If system checks are good, do close out.
   2. If fault remains, continue with next step.

6. Make sure the power from ACPC is received at the avionics Exhaust fan converter.

   1. If there is power, go to step 8.
   2. If there is no power, continue with next step.

7. Replace ACPC.

   1. If system checks are good, do close out.
   2. If fault remains, continue with next step.

8. Swap ACSCs

   1. If system checks are good, do close out.
   2. If fault remains, continue with next step.

9. Replace avionics Exhaust fan converter

   1. If system checks are good, do close out.
   2. If fault remains, continue with next step.

10. Replace Avionics Exhaust fan.
11. Do close out.
    Select an Item:2161529ECS - [ACSC1-A] AV RACK FAN2162529ECS - [ACSC1-B] AV RACK FAN