Over the past couple of years, there have been several queries on various Bulletin Boards or Forums asking for help in determining what the polarity of a particular car is. Someone has purchased an intact MG with no battery installed and they are asking how to tell if the car is the original positive ground or if it has been converted somewhere along the line to negative ground. This may be fairly easy with the later MGBs (one only has to look at how the tachometer is wired. It gets a bit more complicated if it is a T series, MGA or very early MGB, all with mechanical tachometers installed. To further complicate the matter, the car may not have the original coil with the CB and SW markings on it and if the original coil is still there, did somebody not change the hook up when they did the polarity conversion or if it is not wired as original, was that the result of someone wiring the coil incorrectly.
Those of us with cars from the era of positive ground wiring, who are going to convert to negative ground, can do everybody, including themselves a favor by making sure that when the conversion is done a “Negative Earth” sticker is purchased and placed in a very obvious position in their car. Moss Motors and Victoria British both carry two different “Negative Earth” stickers. A 1” X 4” sticker with black lettering on a silver background that is ideal for placing on the bonnet locking platform (aka, slam panel) of the MGAs and MGBs or somewhere on the battery box of the T series cars is available as the following part numbers: M/M 215-650 or V/B 9-0778. A 2” X 4” sticker with red lettering on a silver background and would be ideal to put on the shelf, under the battery cover of the MGBs is available as the following part numbers: Moss Motors 215-655 or Victoria British 9-0832.