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MG MG Y Type - Battery isolator switch

Have always liked to have a battery master switch as an extra safety item on elderly machinery wiring and this appears to be easy to fit on a Y, either on the battery box or on the outside or inside of the bulkhead/firewall. However the YB is the first car I have considered doing this which has positive earth. Am I right in assuming the switch should be between the positive terminal and the earth? Grateful for any advice and experience of such a fitting.
Regards
Geoffrey Wilson
G H Wilson

I am sure it fits on the earth side (positive if your car is original).

Some have been fitted directly to the starter motor as an anti theft device.

Isolating switches that fit on the round post terminals don't fit on positive earth cars because the pole is the wrong size as they are designed for negative earth cars. Battery posts are different diameters apparently so you don't fit the leads the wrong way round.

Let us know how you fit it as its a good idea.
David Mullen

David is right in saying that the proprietory battery isolators designed to fit on round post terminals only fit the negative post. However, provided one or other of the terminals is isolated I don't think it matters which. (Someone is bound to correct me).

Anyway, I fitted one to the negative post of my YA some time ago and its worth it for the peace of mind.
The device fits neatly inside the battery box and enables me to quickly isolate the battery whenever the car is left standing.

Bill
Bill Bennett

Bill,
I'm in the middle of a rewire and an isolator is also on the list.
Where did you get it? Is there a reference?

Thanks, michael
Michael Nicholson

Michael,

Mine came from Vehicle Wiring Products in Ilkeston, Derbyshire <www.vehicleproducts.co.uk> their ref. no. 02100, at £7.62 + p&p + Vat.

Paul Beck at Vintage Supplies <www.vintagesupplies.com> also lists them under ref. no. 886, at £7.60 ++ as above.

I've no connection (sorry!!) with either company.

Cheers

Bill

Bill Bennett

When I rebuilt my YB 10 years ago, I wired in an isolator switch on the bulkhead adjacent to the control box and into the Negative cable. Has worked fine ever since and is easy to get at just by lifting the offside bonnet side. Bracket was a small length of sheet steel and folded to shape. See picture.
Keith D Herkes

OK so I pressed the wrong button!

Keith D Herkes

There's a reason why they should be attached to the earth side but I can't recall who said it to me or what the reason was! - can Neil Cairns help here. I might be wrong though! Maybe something to do with mounting the switch on the car body?
David Mullen

Many thanks to everyone for helpful comments. Have now installed an isolator switch which works fine. We used a Paul Beck switch (part number 463A) fitted on the outside of the battery box adjoining the identification plate so that the connections are inside the battery box and it interrupts the connection between the positive pole of the battery and earth. This is neat and convenient as the switch can be operated by simply opening the nearside bonnet without the need to remove the lid of the battery box.
Regards,
Geoffrey Wilson
G H Wilson

Any chance of a photo?
David Mullen

If you interupt the hot cable instead of the ground it would still be possible to create a short, for example if a spanner touched the body while tightening a nut on the battery switch.
Scott Barrow

David, unfortunately my computer skills don't at present extend to photos but your comment will prod me to do something about that.
Regards
Geoffrey Wilson
G H Wilson

David,
Isolator switch photo now in my computer but how do I get it as an attachment to a comment on this thread. Unfortunately no grandchildren around at the moment to help pre-computer age fossils. But will keep trying.
Regards
Geoffrey Wilson
G H Wilson

Herewith (I hope) photo of isolator switch

G H Wilson

Thanks for the photo-did you use a small earth lead for the battery to switch lead - I have the type with the key
so need a small lead for battery to switch then one for switch to earth(+ve).
David Mullen

We reused the insulated cable from the battery pole but connected it to the switch instead of earth. Then we used flat braided earth cable from the switch to earth - it all fitted neatly on the inside of the battery box
Regards
Geoffrey Wilson
G H Wilson

This thread was discussed between 05/08/2008 and 14/08/2008

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