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Battery Isolator - Advice Please
#1
I’ve recently fitted a starter to my Ulsteroid having lived without one for a number of years. 

I’m now a bit concerned that a 90 year old starter button is the only thing preventing a dead short between the battery lead and earth so had decided to fit a “Red Key” type of isolator switch but can’t find anywhere suitable to mount it.

Originally I was going to mount this on the timber batten which runs across the floor just forward of the battery box and supports the front of the passenger seat.  However I already have a fire extinguisher mounted to the floor just in front of this and combined with the floor mounted starter button this leaves very little room for the switch. (See Photo). 


.jpg   Ulster Isolator 5.jpg (Size: 9.11 KB / Downloads: 514)

It’s actually more cramped than it looks because you need room for the key to operate.  In addition the thickness of the timber means the switch terminals would be partly below the surface so I’d presumably have to router away some of the batten to allow access.

Alternatively I could possibly drill a 23 mm hole right through the timber and then insert the switch from the battery box side with it’s stem passing through the hole and projecting around 10 mm forward to accept the key.  This would possibly work but the switch terminals would then be fairly close to the battery post.

Finally I suppose I could mount the switch up on the dash but this would mean longer, unprotected, cable runs plus an obviously modern switch in full view.

Any suggestions / comments.

John.
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#2
Hi John

This is what I have done on my special.  Apparently it is best to isolate the earth so my earth cable runs from the battery, over the prop (well clipped to the tunnel) and through the driver side seat front.

The cable runs from the switch to the bell housing on the driver side with a separate cable direct to the chassis.

Hope this helps?

Howard


Attached Files
.jpeg   66ABC8F7-61A2-40FA-89E0-459C7646B1DF.jpeg (Size: 85.33 KB / Downloads: 441)
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#3
I plan on fitting this https://www.autoelectricsupplies.co.uk/m...ategory/30

Pricier than on Ebay, but I'm hoping more robust than some. And vrtually no fitting required!
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#4
move the fire extinguisher...?
I found the rotator kill switches better in the end so you don't have to worry about losing the key.
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#5
I have the type that Colin has and I bought mine from eBay some 10 yrs ago without any problems. No extra wiring. Clamps to the battery neg post and the earth strap clamps to the switch. Easy to fit and easy to use.

John Mason.
Would you believe it "Her who must be obeyed" refers to my Ruby as the toy.
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#6
Hi, I also use one like Colin's which I bought several years ago for the Nippy as I had similar issues with where to put the one with the red key which my dad bought for me. The green one took 5 minutes to fit and seems to work really well.
Hope you find a solution soon!
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#7
Hi

I think the battery isolator should be as close as possible to the battery. The type Colin suggests would be good. The problem is that a short can occur anywhere along the cable run and can be upstream from the isolator towards the battery. This would leave a remotely located isolator doing nothing. I would have thought the isolator should be connected to the positive in a neg earth car. Whilst not an "isolator" one of our modern cars has the fuses mounted in a pack directly onto the positive terminal to protect against shorts along the wiring harness.
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#8
I understand the isolator switch is fitted to the Earth terminal? (Negative on my sevens)
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#9
Hi

sorry I think I made a mistake there. It does seem that on a negative earth car the mechanical isolator is in fact put on the negative terminal.

I think it probably follows the correct battery removal procedure - a neg earth car when removing a battery always remove the negative terminal first.

With the isolator I presume it is fitted on the earth side because if you need to isolate the battery and you are having difficulty (device gummed up stuck) and you need to use metal tools on it shorting the neg terminal to earth would have no effect. If the isolator was on the positive and it was stuck then obviously there would be the chance of even more problems.
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#10
Idle curiosity this, but is there any reason for isolating the earth terminal rather than the live side, other than to follow the standard sequence for disconnecting and reconnecting a car battery "Earth, live, live, earth"?
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