EVS DEFOG FAULT
(Advisory)

There is a missing or invalid input of defog set point label from the Head-up Flight Display Computer (HFDC) to the Enhanced Vision System (EVS) heater controller when the EVS infrared sensor unit (ISU) is selected on.

• Head-Up Display (HUD) Computer (A250)
• LH Engine P20/T20 Temperature Sensor (TAT 1)
• RH Engine P20/T20 Temperature Sensor (TAT 2)
• Total Air Temperature (TAT) Probe 3
• EVS Heater Controller (A315)
• Associated Wiring

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

NOTE: CAIMS message 3000142IN - DEFOG FAULT/EVSHC/WRG may display when the CAS message is active.

1. Access the PMAT CAIMS BUS Reader (from the PMAT Start Menu). Add the following signals:

   • Micro Air Data Computer 1 - WSP 9 - STATIC AIR TEMPERATURE
   • Micro Air Data Computer 2 - WSP 9 - STATIC AIR TEMPERATURE
   • Micro Air Data Computer 3 - WSP 9 - STATIC AIR TEMPERATURE

   1. If there is a Static air temperature displayed for all three MADC and the values are the same or very close, go to step 3.
   2. If one of the values is missing or out of range, continue with next step.

2. Perform a wiring check between the affected MADC and its associated TAT probe. Repair defective wiring if required or replace TAT probe.

   • MADC 1 = P20/T20 on LH engine intake
   • MADC 2 = P20/T20 on RH engine intake
   • MADC 3 = TAT 3 on RH FWD fuselage

3. Perform a wiring check between the HUD computer (A250) and the Master Warning/Caution panel (AP15) and the EVS Heater Controller (A315) as follows:
   

   From	To	Result
   A250DP1-D3	AP15P2-D
   A315P1-W	AP15P2-F

   NOTE: Make sure to check for short circuit to ground also on these wires.

   1. If wiring defects are found, repair defective wiring as required and do close out.
   2. If no defects are found, continue with next step.

4. Perform a wiring check between the HUD computer (A250) and DAU 4 (A31) as follows:
   

   From	To	Result
   A250EP1-G6	A31CP1-B2
   A250EP1-H6	A31CP1-C2

   1. If wiring defects are found, repair defective wiring as required and do close out.
   2. If no defects are found, continue with next step.

5. Perform a wiring check between the HUD computer (A250) and the MADCs as follows:
   MADC 1
   

   From	To	Result
   A250BP1-J1	A27P1-68
   A250BP1-K1	A27P1-69

   MADC 2

   From	To	Result
   A250EP1-E1	A28P1-68
   A250EP1-E2	A28P1-69

   MADC 3

   From	To	Result
   A250EP1-E4	A29P1-66
   A250EP1-F4	A29P1-67
   A250BP1-E6	A29P1-63
   A250BP1-F6	A29P1-64

   1. If wiring defects are found, repair defective wiring as required and do close out.
   2. If no defects are found, continue with next step.

6. Perform a wiring check between the EVS Heater Controller and the Infrared Window (IRW).
   

   From	To	Result
   A315P1-BB	A320P1-G
   A315P1-KK	A320P1-C
   A315P1-a	A320P1-A
   A315P1-Z	A320P1-B
   A315P1-Y	A320P1-J
   A315P1-X	A320P1-K

   1. If wiring defects are found, repair defective wiring as required and do close out.
   2. If no defects are found, continue with next step.

7. Swap DAU 4 with DAU 2. Is the fault still present?

   1. If YES, continue with next step.
   2. If NO, replace defective DAU.

8. Replace the IRW. Is the fault still present?

   1. If YES, continue with next step.
   2. If NO, do close out.

9. Replace the EVS Heater Controller.Is the fault still present?

   1. If YES, continue with next step.
   2. If NO, do close out.

10. Replace the HUD computer.
11. Do close out.