Battery Ground Cable
Failures and fixes
On several Mark III's the battery ground cable has broke, causing loss of power. In the cases addressed here, the eyelet that attaches the cable to the frame has snapped off. The following photos show what may be the root cause of these failures. Below are 3 ways to help prevent a failure
These photos are of SPF 1265. At the time of the photos, it's seven years old and has about 30,000 miles. The cable shown is new. I suspect that this condition of the trunk floor, shown above, pushing down on the eyelet is something that got worse over time with the body settling down on the frame. It is likely the trunk floor pushing down on the eyelet and the vibration of normal driving fatigues the eyelet until it fails.
A quick fix is to bend the eyelet so it is no longer pushing up on the floor of the trunk.
With just a little more effort you can enlarge the hole and improve the clearance between the eyelet and the floor
Probably the best fix is to shorten the attaching boss. If you go this route, you can skip the first two options. This option is more difficult because of the boss location. After shortening the boss you also need to tap the bolt hole deeper. The hole extends all the way to the frame member that it's welded to, but not the threads.
This is the results after the boss was shortened.
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