Improper wiring induced fault

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2 weeks 4 days ago #1599 by dynamics
Is it possible that improper condition of airplane/CSD wires cause low oil pressure light in flight deck illuminates whereas CSD oil pressure switch is open (pressure is not low)?

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2 weeks 4 days ago #1601 by Mark
Replied by Mark on topic Improper wiring induced fault
Come on over and work on some of these "old" 767's that I work on. You'll get your fill of bad wires and wires shorted to ground.

The CSD oil pressure switch only plays a part in indication and not control. The switch provides a ground to the overhead annunciator. This will also illuminate the "Master Caution" light. It will not cause the CSD to disconnect or change its functions in any way.

If the light is flickering..... you're picking up a ground on the signal wire from some other area. The most suspect areas are the engine itself, pylon, or wing root.
  
  
 
  
  
If your mechanics are interpreting this as the CSD is low on oil and constantly filling (overfilling), the CSD will run hot and fail early.

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2 weeks 4 days ago #1602 by Mark
Replied by Mark on topic Improper wiring induced fault
The crews are probably doing what is required in the abnormal procedures book and disconnecting the CSD.

You get a write-up stating high oil temp warning with a manual disconnect completed. This does not mean the CSD is bad. It just means the crew reacted properly.

Your best tool for troubleshooting shorts is a Megger. Disconnect the plug from the CSD and meg from the overhead annunciator panel pin that comes from CSD to ground. Shake some wires around while someone is watching the megger. Look at the condition of the plug that connects to the CSD itself. We've found pins shorted internally.

The print above is not your effectivity...... but it shows pins 7 & 8 at that plug. They're right next to each other. If the megger shows a short, punch a pin out to see if it goes away.
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