Classic cars forum & vehicle restoration.

FAB Cruiser · Joined: 03 Jul 2008 Posts: 77

My car came with one of these switches bolted to the bulkhead and attached via an earth strap to the negative terminal. It's the type with the removable red key and the car is negative earth.

I want to change it to isolate the positive terminal instead so that I can put a bypass across it for the alarm to work when the key is removed.

How do these keys work on the positive side? i.e.does it just 'float' in line on a cable. I can't imagine how it would attach if not bolted to the bulkhead unless they make a different type for positive terminals.

Hope this makes some kind of sense!!

Thanks
David

Phil - Nottingham · Joined: 01 Jan 2008 Posts: 1252 Location: Nottingham

The ones I have seen and one I have have got, the key just presses 2 contacts togther, they can in theory be placed in either earth or live side but for safety it should be in the live.

The body of the switch should be insulated from the contacts
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Greeney in France · Posted: Sun Jan 25, 2009 5:55 pm Post subject:

Yes the same here in France they are for sale everywhere even in supermarkets and work on the positive terminal as they are insulated from the body
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FAB Cruiser · Joined: 03 Jul 2008 Posts: 77

Understood. The ones I've seen have two screw terminals. I can see how to put it in the live circuit but how do you mount the switch. Won't it just flop about? Because my one is currently on the negative side, it has an L bracket from one terminal to the body.

Sorry for being thick, but I can't find any pictures online.

Cheers
David

Phil - Nottingham · Joined: 01 Jan 2008 Posts: 1252 Location: Nottingham

Its meant to mounted on a steel panel eg bulkead/floor/kickplate. One large hole for the centre and 2 small holes to bolt/screw it down. It is best to use proper insulator caps on the terminals.

Clearly it has to be mounted accessibly but out of where it can be kicked + if you have a fused shunt where you can access it

Like this

http://www.roverp4dg.org.uk/phpBB2/viewtopic.php?t=848&postdays=0&postorder=asc&start=0
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Penman · Joined: 23 Nov 2007 Posts: 4757 Location: Swindon, Wilts.

Hi
I don't know if it was + or - earth but I have seen one at least mounted straight onto the battery.
Could you fix the bracket to the battery terminal fitting and then the battery lead to the terminal on the switch

pigtin · Joined: 23 Nov 2007 Posts: 1879 Location: Herne Bay

You can buy them incorporated in the battery terminal, seen them for sale somewhere but can't remember where. Confused

Don.
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Greeney in France · Posted: Mon Jan 26, 2009 11:13 am Post subject:

They are everywhere here I don't think the French know about alarm systems
Range from a tenner to 20€ if you want one picking up just say. Even the supermarket sells them lol
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47p2 · Joined: 24 Nov 2007 Posts: 2009 Location: Glasgow

I have a marine version of a cut off switch fitted under the bonnet of my P2. When I bought the car I lost my storage about a year after and had to put it into commercial storage. The owner of the storage insisted I disconnect the battery. This meant taking out the rear seat which is a pain in the neck so I did a compromise and fitted the switch under the bonnet by fabricating a couple of L shaped brackets and using existing bolts to mount it close to the solenoid.
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Phil - Nottingham · Joined: 01 Jan 2008 Posts: 1252 Location: Nottingham

On my Rover 16 I mounted the switch on the front of the rear seat base where it can just be reached from the drivers seat. It only meant diverting the positive lead to one side of the switch and a new short length from the battery terminal to the switch.

On a Renault 12 and a 14 I had in the 1970's the battery terminal clamps had plastic hand screws on top that just needed a quarter turn to disconnect them. These were standard fit and were a really good idea
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FAB Cruiser · Joined: 03 Jul 2008 Posts: 77

Thanks for all the ideas guys.

I've found one that attaches to the positive terminal and has a green wheel that you turn to disconnect.

There's also a version with a fused bypass across it for the alarm. Should do the trick nicely.

Cheers
David

FAB Cruiser · Joined: 03 Jul 2008 Posts: 77

Just got back onto this topic today. Check out the green isolation switch with bypass in the link below:

http://shop1.actinicexpress.co.uk/shops/Rat_Sport/index.php?cat=Terminals___Leads

Does this item miss the point?

Surely the fused bypass allows a current to flow when the car is garaged, hence the battery isn't isolated and it will still drain over time?

And although I can see how the fused supply would keep the radio and alarm live at all times, if you forget you've left the switch in the off position (Which I would do regularly!!) won't it blow the fuse when you crank the starter?

Surely the bypass should connect at the battery terminal and then go directly to the alarm and radio without connecting to the other side of the switch?

BTW, I'm assuming this would be on the positive side with the earth permanently connected.

Cheers
David

Phil - Nottingham · Joined: 01 Jan 2008 Posts: 1252 Location: Nottingham

Batteries self discharge anyway - the isolating switch is for safety really

. Connecting direct would not prevent loom insulation leakage in the main battery circuits as the shunted live radio/alarm could then supply the rest of battery fed supplies unless care was taken to make sure they were direct supplied on a dedicated circuit - on a older classic this is reasonably easy to do
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Bugly · Joined: 25 Jan 2009 Posts: 65 Location: Darwin, Australia

Good evening all -

The battery isolator with the green wheel and the fused shunt is designed to allow the low-current devices such as clock and alarm to still work through the fuse, but will stop any attempt to start the car, as the fuse will blow due to the higher current drain.

If full battery isolation is required, you would need to either remove the shunt, or buy an isolator one without one.

Cheers - Bugly