Isolating engine and electrics with one switch.

[uqunder10s]

I need to install an externally operated kill switch which will isolate the batteries on my Patrol, and I would like it to cut the diesel engine as well. I would like to install only 1 switch, the batteries are connected under the bonnet by a dual battery management system which I would like to retain for normal use.

I intended to install a couple of posts under the bonnet to connect the current battery earth returns to. Then run these posts to a common switch, and run the switch to the negative battery posts (see attached sketch). The idea being that if I cut the earth then the circuit is broken, without the need to mess around with the positive side where the dual battery management system is. I can also easily render the switch inoperative (for when using normally around town) by relocating the earth returns directly back to the battery.

I have been advised that the engine should shut down at the same time as battery isolation for safety reasons and to prevent an unregulated voltage from the alternator damaging electronics. I thought that since the earth loop of the electrical system would be incomplete then the fuel shutoff solenoid would close and shut down the motor but some testing this weekend showed is not the case, so I assume the solenoid remains energised by the alternator.

My questions are:

How come the solenoid doesn’t need an earth to stay active (or does the alternator maintain a 0v side?).

How can I get the solenoid to shut off at the same time?

Cheers

Steve

[Woop]

Steve,

Could you use a Marine type battery switch that has an Alternator Field disconnect built in? Instead of using it to disconnect the alternator, why not use it to cut power to the Fuel Solenoid instead......

NickW