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Battery cut-off switch wiring that I just don't understand

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Luegolover Avatar
Luegolover Steve L
London, London, UK   GBR
Hello,

I have a standard BN1 wiring loom and Lucas battery cut-off switch and I just can't get my head round it hence I'm asking for someone to explain what is probably blindingly obvious. Anyway, here goes.

My switch has three terminals. One connects to the battery, one to ground and one to the loom and from there on to the coil and distributor. Now when I use a meter to check the operation of the switch I find that when turned on the battery side connects to the ground side and this I understand. The coil side isn't operational when in the state. When it is switched off the battery side connects to the coil terminal. This I don't get, why would it do that?

Any idea's?
Is this normal?

Thanks in advance
Steve

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RTaillieu Avatar
RTaillieu Rick Taillieu
Leamington, ON, Canada   CAN
Steve,

When you turn the switch to "OFF" it grounds the wire to the coil so the car can't be hot-wired.
If yours is connected to the battery you have the large cables to the battery and ground reversed



Rick
'64 BJ8 P1
'69 E-Type 2+2



Edited 1 time(s). Last edit at 2018-12-23 05:46 PM by RTaillieu.

Luegolover Avatar
Luegolover Steve L
London, London, UK   GBR
Thank you Rick,

I haven't fitted the switch yet, doing so today, but had made the assumption as to what way the cables connected to the switch and obviously made the wrong assumption. I understand now, thank you for patiently explain the blindingly obvious to me.

Steve

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brims49 Andrew Brims
Peachland, BC, Canada   CAN
Hello Steve, When the main terminals of this switch are open, ie in the OFF position, the coil is grounded out through this switch( closed terminal) rendering your motor tamper proof. My understanding of this anyway.
Merry Christmas

Rob Glasgow Avatar
Lompoc, CA, USA   USA
I always thought the switch design was kind of a belt and suspenders deal. If you've switched off the power from the battery, how are you going to hot wire the car? You've got no juice to start it anyway.....oh I guess if the thief brought along another battery, some jumper cables opened the bonnet, attached the cables to the solenoid, the coil grounding function would be effective. Most likely he'd just bring a flat bed tow truck and load the car on the back and away he'd go.
That being said, I do shut off the cut off switch and lock the trunk if I'm going to be away from the car for several weeks. But I'm more concerned about having the car being burned in a house fire when I'm gone than it being stolen.

Luegolover Avatar
Luegolover Steve L
London, London, UK   GBR
Well it's installed, thanks for your help.


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