Message Name:

OPEN CIRCUIT

Message Code:

B3-007666

Associated CAS:

R BLEED LOOP FAIL
(Caution)

BLEED LOOP FAULT
(Advisory)

The RIGHT BLEED LOOP is detected open circuit by the IASC-2 during the system self-test. Check the loop and wiring continuity to ground.

• R Bleed Duct Leak
• R Bleed Loop Sensor 1 (MT38)
• R Bleed Loop Sensor 2 (MT40)
• R Bleed Loop Sensor 3 (MT71)
• Associated Wiring

Advisory Wire/Service Bulletin:

• AW300-36-0310 - Bleed Loop Connector Cleaning Tool

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 25 and 26. Resistance should be approximately 37.8 ohms.
3. Isolate a system short through standard practices by isolating the three* 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.
   RH BLEED LOOP Schematic and Resistance Values

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 ohms 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.

NOTE: Dirty contacts can lead to an increase in the loop resistance values to the point of tripping a BLEED LOOP FAULT CAS/OPEN CIRCUIT B3 message. Make sure that all connectors of the applicable loop are clean.