Quote:
Originally Posted by rsisk
If there was a short with the frame, does this mean the frame isolation test during inspection was not done?
Or would this happen even if the frame isolation test passed?
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There's a lot of variables that can go into this, we can't say for certain if it was or was not done. It's possible it was done, but after the fact the insulation wore through. It's possible the frame short was intermittent, and only occurred when a wire was pinched in a mechanism a specific way. Or the team was doing a hasty repair and pinched a wire, or drilled through the insulation of a wire, or disconnected a motor and had the leads just dangling... There are any number of ways for the frame to short out either before or after a frame isolation test is done. And most of the time the frame isolation test is not performed during reinspection.
The reason we do the frame isolation test is to ensure that it takes two faults to cause a problem, not just one. Two faults obviously can still happen, but it's half as likely to happen as having one fault.