Kill Switch question

[Paul.B]

Is there any reason why I can't install a kill switch on the -ve side of a cars electrical system? I know on the +ve side you need to add the extra wiring to take the alternator discharge through a balast resistor to earth but what about on the -ve side?

The car will have a modern ECU and electric fuel pumps etc. Am I right in thinking by disconnecting the -ve will kill the engine? If not why?

Cheers

[anonymous-user]

which ever "side" you choose to disconnect, you need to deal with the inductive energy stored in the magnetics of the spinning alternator at the moment of disconnection. if you don't Vbatt can spike up to over 100V, which even with the battery disconnected maybe enough to kill any electronic device in the system!

[stevieturbo]

Wire it in as most motorsport types require....its tried and tested

[Paul.B]

Cheers guys. I'll not wander off the tried & tested route!

[Mr2Mike]

Paul.B said:

Is there any reason why I can't install a kill switch on the -ve side of a cars electrical system? I know on the +ve side you need to add the extra wiring to take the alternator discharge through a balast resistor to earth but what about on the -ve side?

The car will have a modern ECU and electric fuel pumps etc. Am I right in thinking by disconnecting the -ve will kill the engine? If not why?

Cheers

It won't work for the same reason it doesn't work on the positive side, the alternator and ignition/ECU all share a common ground, so simply disconnecting the battery -ve will not prevent the alternator from continuing to power everything.