Message Name:

SHORT CIRCUIT

Message Code:

B3-008099

Associated CAS:

BLEED LOOP FAULT
(Advisory)

WING A/ICE LOOP FAIL
(Advisory)

The LEFT PYLON / WING LOOP is detected shorted to ground by the IASC-2 during the system self-test. Check the loop and wiring isolation to ground.

• L WAI/Pylon Loop Sensor 1B (MT45)
• L WAI/Pylon Loop Sensor 2B (MT47)
• L WAI/Pylon Loop Sensor 3B (MT49)
• L WAI/Pylon Loop Sensor 4B (MT51)
• L WAI/Pylon Loop Sensor 5B (MT103)
• L WAI/Pylon Loop Sensor 6B (MT119)
• Associated Wiring

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

Bleed Loop Routing and Visual Aid Guide

Troubleshooting Guide for Bleed Loops

NOTE: If the bleed loop resistance value is within limits try cleaning the bleed loop connections per SPM 51-25-00-110-801 and then reapply lubrication to the connections per SPM 20-20-00. Lubrication part number is called out in each bleed loop installation procedure. Run the aircraft after the cleaning and applying lubing procedure and see if the BLEED LOOP FAULT clears.

1. Gain access to IASC #2 located behind the lavatory sink just forward of the water pallet.
2. Disconnect connector A56P4 from the IASC and check resistance between pins 1 and 6. Resistance should be approximately 67 Ω.
3. Isolate a system short through standard practices by isolating the six* different loops and wiring from the IASC. Repair faulty wire segment or replace loop as required.
   *Only the first loop is identified, the IASC and MDC can not identify which section of a multiple loop segment is at fault during a short or open condition and will only list the first loop of the segment.
   L Pylon and Wing Loop Information
   L Pylon and Wing Loop Schematic

   1. Perform resistance checks on the applicable loop per AMM 36-21-00-760-801.

NOTE: Measure Insulation resistance and line resistance of the detection loops as per the Leak Detection Elements troubleshooting sheet. Make sure line resistance & insulation values are within the specified limits.

NOTE: Often while troubleshooting this discrepancy the CAS is not usually present. However what you may find is higher than normal resistance such as 10 Ω or higher above nominal. It is not high enough to trip a bleed loop fault CAS message but high enough to assist in troubleshooting. When you get the resistance value down to nominal values then it is safe to say you've corrected the discrepancy.