Fitting a Kill Switch to a Positive Earth 1963 Series IIA

[GeorgetheLandy]

So I have had good reason to want to fit a kill switch to my 1963 Series IIA but before I do I wanted to double check I was travelling down the right path...  I did some research and according to all the reviews the remote controlled kill switches are really not that reliable, in some instances leaving people stranded, though how that happens is a little beyond me but there you go.  So I opted for a manual switch with removable key.  They don't seem to be theft proof though as if anyone who is determined found it I am sure they can figure it out and buy a spare key, so really need to think about a clever placement unless anyone has any better suggestions on switches this seems to be the most reliable. https://www.pegasusautoracing.com/productdetails.asp?RecID=1465

The question I have is, is it okay to use the positive lead as the main line into the kill switch or does it have to be the negative lead on my car due to it being a positive earth?  I am not an electrician and know only very basic wiring skills, so just want to make sure that A. This is a good switch to use and B. I am okay using the positive lead as the lead to disconnect?

Thanks in advance for the responses and advice.

G

Edited April 18, 2022 by GeorgetheLandy

[GeorgetheLandy]

9 hours ago, GeorgetheLandy said:

So I have had good reason to want to fit a kill switch to my 1963 Series IIA but before I do I wanted to double check I was travelling down the right path...  I did some research and according to all the reviews the remote controlled kill switches are really not that reliable, in some instances leaving people stranded, though how that happens is a little beyond me but there you go.  So I opted for a manual switch with removable key.  They don't seem to be theft proof though as if anyone who is determined found it I am sure they can figure it out and buy a spare key, so really need to think about a clever placement unless anyone has any better suggestions on switches this seems to be the most reliable. https://www.pegasusautoracing.com/productdetails.asp?RecID=1465

The question I have is, is it okay to use the positive lead as the main line into the kill switch or does it have to be the negative lead on my car due to it being a positive earth?  I am not an electrician and know only very basic wiring skills, so just want to make sure that A. This is a good switch to use and B. I am okay using the positive lead as the lead to disconnect?

Thanks in advance for the responses and advice.

G

Okay, just decided after a little more research that it's best to install the kill switch on the positive lead, breaking the positive supply, so unless I hear otherwise that is how I will wire it.  Also heard that fitting an on/off switch to the positive wire from the coil has a similar effect.  Thoughts...

[Bowie69]

What are the reasons for fitting, just security? 

[smallfry]

As long as there are no earths bypassing the switch, it will be fine. I can see no reason why you could not fit it to the negative lead either, again, as long as it is not bypassed somehow.

If it is for security though, these are so easily to get around unless it is installed in a secured, or inaccessible space. 

[GeorgetheLandy]

6 hours ago, Bowie69 said:

What are the reasons for fitting, just security? 

Security and convenience when working on the engine.  I recently took it out for a run and when I returned to where I parked it somebody had tried getting into it; the door had been opened.  Also just want a convenient way to disconnect the battery when working on the car.  

[GeorgetheLandy]

3 hours ago, smallfry said:

As long as there are no earths bypassing the switch, it will be fine. I can see no reason why you could not fit it to the negative lead either, again, as long as it is not bypassed somehow.

If it is for security though, these are so easily to get around unless it is installed in a secured, or inaccessible space. 

Yes, that was also part of my worry so I will have it in a secure and remote place. Also going to fit a switch to the ignition coil too.

[FridgeFreezer]

Those red plastic switches are not renowned for reliability - the far chunkier metal & bakelite versions are a big improvement.

Also, be aware that single contact switches should not be used to "kill" a running engine as you remove the alternator's reference, which can allow it to run away and fry electrical components. I have a very crispy Megasquirt ECU in my shed from someone who found this out.