classic motorcycle forum

Motorcycle Discussions => British Bikes => Topic started by: MyT21 on December 11, 2007, 04:45:44 PM

Title: +VE AND -VE EARTH SYSTEM
Post by: MyT21 on December 11, 2007, 04:45:44 PM

HI guy,

Does anyone can explain what is the different/important between these 2 method of earth system to the rest of electrical equipment specifically..(coil,distributr,alternator,batt,etc)

Recently,I did a wiring on my t21 bike and If I were to change from +ve earth(as in diagram) to -ve earth just because of our norm here is to use -ve earth ,then would there be any harm to others electrical parts?
My idea is either +ve or -ve,it just to provide a complete flowing path of the current..

your input is highly appreciated.
cheers

Title: Re: +VE AND -VE EARTH SYSTEM
Post by: twolitre on December 11, 2007, 06:43:58 PM

There is no practical advantage either way unless you are going to start using solid state electrical equipment (containing for example diodes or transistors) which is usually -ve earth because manufacture of those components with -ve earth is easier.  Most British vehicles were +ve earth well in to the fifties/early sixties - I believe the argument being that all electrolytic corrosion was concentrated on the +ve battery terminal where it was easily cleaned off instead of a little corrosion on every terminal around the vehicle.  Of course solid state electronics were yet to be invented.
  You cannot change your bike over without changing rectifier wiring over and in some cases changing the rectifier.  I would say stay with +ve earth unless you need to change it.
  If you do change over by swapping the rectifier or its connections, everything will work but the ammeter leads will need changing over to stop the ammeter reading backwards and the ignition coil leads need changing over to maintain ignition efficiency.