The Master switch on my car was always on the positive side of the battery, however I read recently that some people connect this switch on the negative side of the battery.

If anyone uses this switch, which side of the battery do you all connect to?

cheers

kenny.

 

got to be on positive!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! otherwise everything is still live if it cuts neg!!!!!!!!!!!! also must use a shunt!! otherwise alternater will keep charging when or if!! your upside down !
see your scrutteneer- blue book etc etc

 

Hi Aaroncast

The 3 Ohm shunt resistor is no problem, I've had it connected since I wired the car 3 yrs ago.

Perhaps the book I read was a bit old and a little out of date?

Everything at the same protential is the outcome, so being at Gnd or +12V is relative. It could be wired both ways.

The reason I asked was that I could not see a benefit of switching the neg side.

 

I guess it could be easier to fit on the neg as you've less wires and also so you can keep the fuse box bolted on the positive side if still required on the car.

 

Switch the positive.

The +ive coil feed should then be cut through pins 1 on the smaller circuit.

No real need to use the resistor on pin 2. It's there to prevent damaging the alternator by 'sinking' the excess current to earth.

In reality in that split second you'll have fuel pump, ecu fan etc etc running which will do this, so no halm will be done.

Its only really neccesary on older cars which aren't running anything that could sink the current.