HT coil polarity

[lancialulu]

Any thoughts as to why HT coils are marked + / - as the primary is isolated from the secondary and case normally?

Just that I found my Aprilia CB connection wired to the positive not negative (neg earth car)?

Normal convention is contact breaker lead goes to neg if neg earth car....

Tim

[welleyes]

If you have the terminal connected the “wrong” way, the side electrodes of the plugs will erode more quickly. Books sometimes describe the correct way of connecting as “essential.” In fact, it is not very significant. Older Citroens and Harley Davidsons use double ended coils, the construction of which means that one plug has the “correct” polarity and one has the “incorrect.” Considerable numbers of Morgan three wheelers have run for a generous lifetime on double ended coils.

Stuart Tallack p.p. Andrew Tallack

(Apologies for lack of accent on Citroen.)

[lancialulu]

With Stuart/Andrew prompting further googling I found this quite helpful article.

http://mgaguru.com/mgtech/ignition/ig104.htm

Tim