I, too, would like to know why coils are mounted upside down.
A quick search across various automotive forums reveals that this is a surprisingly common debate—and one that is difficult to pin down with a definitive answer. It turns out that some coils genuinely do have a specific directional requirement based on their internal construction. For example, older Volkswagen coils must be mounted vertically (towers facing down) because their internal ballast resistor needs to be constantly immersed in oil; otherwise, it risks overheating and failing.
However, that doesn't seem to be a universal rule, particularly when we look at our own AD-series trucks. We have plenty of examples of coils mounted in both directions, seemingly functioning just fine either way.
It becomes pretty clear that this debate has been rolling on for decades, long before the internet even existed. But now, coupled with the current mountain of conflicting advice, half-truths, and general "BS" encountered online today, it feels like a question we may never get a straight, universally accepted answer to.
