Perhaps my skill level in electrical engineering is too advanced compared to my knowledge of electrical theory.

To install my start button I picked up power from one of the ignition-live cables from the key barrel. Later I used that same cable for a relay to toggle my cigarette lighter. Same cable is now connected to the toggle switch on my dash, from which I plan to connect up a number of 12v accessories - footwell lighting and so on.

My question(s) are: am I running too much on this one cable in the dash; and will doing so affect the functioning of anything on that circuit (or will worse problems occur)? Would I better off wiring up an entirely new loom that runs directly to and from the battery?

Please explain like I'm 5

Do you mean that the line the switched side (the one that is activated by the relay) will be used for the accessories or will it be the line that is doing the switching?

Do you mean that the line the switched side (the one that is activated by the relay) will be used for the accessories or will it be the line that is doing the switching?

Atm it's the main line from the key barrel which will is the source for everything, including the accessories. Very crude drawing of how everything works atm:

I'm on my phone so I can't really draw a diagram, which I've always been crap at anyway, but if I understand rightly, you're currently wanting 3 ways to run your accessories with power:

1 is through ignition barrel as stock

2 is through start button which will activate a relay to turn on the cig lighter and accessories

3 is toggle switch to activate accessories

Is that correct? If so, I believe you should be fine, I would perhaps get a small fuse box depending on how many different things you're running off the line and fuse each individual circuit appropriately.

I assume you have used the thicker of the power wires that goes into the back of the ignition barrel?

As long as you have used an equally thick wire to run everything else then it shouldn't be an issue. I would however think about installing an inline fuse as if you do try and pull too much current you will only loose the accessorise and not anything for the car itself.

I'm on my phone so I can't really draw a diagram, which I've always been crap at anyway, but if I understand rightly, you're currently wanting 3 ways to run your accessories with power:

1 is through ignition barrel as stock

2 is through start button which will activate a relay to turn on the cig lighter and accessories

3 is toggle switch to activate accessories

Is that correct? If so, I believe you should be fine, I would perhaps get a small fuse box depending on how many different things you're running off the line and fuse each individual circuit appropriately.

Not exactly, I'll try and explain a different way. The 3 main things that come off the original line are Start button, Relay and Toggle switch, but they're all independent - black lines in the pic are just ground wires that I've spliced together, because I figure a ground is a ground My goal was just to get those main 3 ignition-live (which seems to work fine), and then all the accessories will be connnected only to the toggle switch, but my concern is how everything can ultimately be traced back to that first wire from the keybarrel, and if having so much which is all powered by that one 12v line will cause any issues.

I assume you have used the thicker of the power wires that goes into the back of the ignition barrel?

It's quite a thin wire IIRC all the key barrel wires are all about the same size except 2 thick ones which I presume go to the starter. I didn't actually check them, but I've got them connected to the start button which does work

Edited 24 August, 201511 yr by Vio

Sorry old mate, but I'm not understanding your diagram one little bit !

You say that the start button works, but you also say that the black wires are all earth's (ground) - Your diagram is showing the 'output' from the start button going directly to earth, this would blow the fuse if there was one, or burn out the wiring if there wasn't.

Is the earth connection on the toggle switch for illumination purposes?

With regards to the relay, where does the top '+ve' connection come from? the diagram shows it permanently live. Also I take it that this wire is the feed to the relay contacts, the other '+ve' from the ignition switch feeding the relay coil??

It is not good practice to connect lots of accessories directly to the ignition circuit, as there is a danger of starving the ignition coil. If you are going to wire a lot of current (not voltage) hungry items in there, then you need to wire a feed to a relay coil from the toggle switch (the other side of the coil, obviously going to earth) - the ignition system then would be only feeding the relay coil.

All of your 'useless things' would be fed from a positive (+ve) supply via the relay contacts.

If you need a 'heavy-ish' +ve supply, it is better to take that either from an existing fuse, or connect it to the starter motor main +ve terminal, this prevents the risk of corrosion that you might get if connecting directly to battery +ve

As someone else has mentioned, you really should consider placing a fuse in these circuits.

The cross sectional area of the cable that you will require, depends upon the electrical load that you intend to put on it, as does the rating of the relay contacts.

You might find it useful to download the catalogue from www.vehicleproducts.co.uk

Regards

You say that the start button works, but you also say that the black wires are all earth's (ground) - Your diagram is showing the 'output' from the start button going directly to earth, this would blow the fuse if there was one, or burn out the wiring if there wasn't.

There are 2 bits to the start button - the button itself and a control box, the latter has 2 blue wires which connect to the starter circuit and starts the engine. The +ve & ground wires on the diagram just power the box which does the starting, and the light on the button itself (basically it's wired up as per the MightyCarMods video which I used as a reference)

Is the earth connection on the toggle switch for illumination purposes?

Yup. It also has a third pin which would power accessories with the same input, but it's not connected to anything as yet.

With regards to the relay, where does the top '+ve' connection come from? the diagram shows it permanently live. Also I take it that this wire is the feed to the relay contacts, the other '+ve' from the ignition switch feeding the relay coil??

Top +ve is the original cigarette lighter +ve which was permanent live, I wired in the relay so it would be ignition-live. Above is correct ^

It is not good practice to connect lots of accessories directly to the ignition circuit, as there is a danger of starving the ignition coil. If you are going to wire a lot of current (not voltage) hungry items in there, then you need to wire a feed to a relay coil from the toggle switch (the other side of the coil, obviously going to earth) - the ignition system then would be only feeding the relay coil.

All of your 'useless things' would be fed from a positive (+ve) supply via the relay contacts.

If you need a 'heavy-ish' +ve supply, it is better to take that either from an existing fuse, or connect it to the starter motor main +ve terminal, this prevents the risk of corrosion that you might get if connecting directly to battery +ve

As someone else has mentioned, you really should consider placing a fuse in these circuits.

The cross sectional area of the cable that you will require, depends upon the electrical load that you intend to put on it, as does the rating of the relay contacts.

You might find it useful to download the catalogue from www.vehicleproducts.co.uk

Regards

This is exactly what I needed to know. Many thanks

Edited 25 August, 201511 yr by Vio