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MG MGB Technical - Positive or negative ground??

Hi, I have a '55 mgtf with a '65 MGB motor and drivetrain. I intend to install a Moss electronic ignition kit. I was just wondering what the pluses and minuses of changing the positive ground system to a negative ground? I need to know the benefits or problems of the switch before buying the kit. It just seems strange to have a positive ground system. Am I crazy? thanks, Don Baker, Burleson, Texas
d.g. baker

Don - there is no compelling reason to leave a vehicle positive ground other than originality and you have taken car of that with a MGB engine in a TF. I would go ahead and change the car over to negative ground and then if you later want to add a big stereo system or whatever, there will be no problem. With a TF there is no real problem doing the conversion - just reverse the connections to the primary terminals of the coil, reverse the connections to the ammeter, flash the generator to the reverse polarity and check the fuel pump for a diode/resistor assembly or for any solid state conversion. See the article, Polarity Change in the Other Tech Articles on my web site at: http://homepages.donobi.net/sufuelpumps/

finally, do yourself and any future owner a favor and put "Negative Ground" stickers next to the battery to alert anyone working on the car that the polarity has been changed see the article, Negative Ground stickers in the same section as above on my web site. Cheers - Dave
David DuBois

Not strange, standard until the Mk2 MGB of 1967. At least no stranger than anything else on a British car that may be different to what you are used to.

Converting to negative ground will also allow a much easier change to an alternator, which would seem the next logical step.

As well as checking the pump you must be aware of any other polarity-dependant stuff you may have, which could also be damaged by a polarity change. Starters aren't, heater fan shouldn't be on that, wipers may be. Neither of the latter two will be damaged but if the heater fan runs backwards it may not be as effective (or should I say be even more ineffective?), this is the case on the MGB. Wipers may park in a different place, that is if they park automatically anyway ...
Paul Hunt

"if the heater fan runs backwards it may not be as effective (or should I say be even more ineffective?), this is the case on the MGB. Wipers may park in a different place, that is if they park automatically anyway ..."

On T series cars, heaters are what are commonly referred to as a heaver coat, preferably with fleece lined gloves and wipers are all parked manually - nothing polarity sensitive there :) Cheers - Dave
David DuBois

One further note regarding polarity sensitive components in a T series car. the original fuel pump in either the TF 1250 or the later 1500 were all, what is being referred to today as dual polarity (ie. not polarity sensitive), but may well have been replaced with one of the pumps from the past 15 or 20 years that have a Diode/resistor assembly for arc suppression or maybe even one of the later, all electronic pumps, both of which are polarity sensitive. Cheers - Dave
David DuBois

This thread was discussed on 02/11/2008

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