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Author: BenjaminNelson via YouTube
Go to Source
I think I found the source of my problem in my 2013 Tesla Model S.
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After getting the modules out of my battery pack, I could inspect the umbrella valves. These are essentially pressure relief valves on the bottom of the pack.
Battery modules #7 and #10 are near the front of the pack, immediately behind the front tires. This is probably the dirtiest location on the bottom of the car.
I think that dirt and other foreign materials got into the umbrella valves, causing them to be stuck open. That then allowed moisture (driving through puddles, etc.) into those sections of the battery pack.
See all the videos about repairing this car at: https://www.youtube.com/playlist?list=PLmHss3DBZUinXAtGsho-xSke6Wy0M0sWe