Relay Wiring for Independent Lights etc

Hi all,

I am wiring in some additional lights on a friends 110 which are to be completely separate from the existing lighting circuits.
I am planning to wire them as in the diagram I have carefully drawn in Paint and attached to this post.

I have basically copied the wiring from my spot lights, with the exception that the switch was connected to a live from the main beam headlights. I know this works as it is presently running my air horn.


My only concern is with the switch cable. As you can see from the diagram, I intend to use a spur off the live feed from the battery to make the switch work.


What I want to avoid is wasting power/melting the cable to/from switch by it taking to much current.

From my understanding of electricity, if I use the same small cable to ground the relay as I intend to use to/from the switch then the switch wire should not be taking a lot of power? (Potential difference?)

The live will be fused at the battery end in the battery box.

If my diagram is a disaster waiting to happen then please let me know. As I said, I have just copied the wiring of my spots and found a new power source for the switch. It works for my air horn.


Just want the thumbs up that this is a safe solution. Any alternative ideas are very welcome.


Cheers,


Soms.

Yer circuit will work fine.
The current taken by the switch is dictated by the impedance of the relay coil and for a 12V relay will be 0.1A. It has nothing to do with what wire you use.
Use thick wire from the battery to terminal 30, then piggyback thin wire to the switch and back to terminal 86.
Use thick wire for all the other connections, including the earths.

Cheers for the reply. I didn't realise the relay limited the switch current.

I have cable in 1mm, 2mm, 3mm and 4.5mm square sizes so using the correct size shouldn't be a problem. I just need to find out what ratings the bulbs are to choose the cable. I expect 3.0mm2 will do since that is suitable for up to 27.5A.

If the calculation watts = volts x amps is to be used that would cater for up to 330 watts.

The lights being fitted are two work lights which I believe may each have double bulbs. I will have to get hold of them and see what there all about.

They are being fitted to the front bumper so it will be an easy job bar drilling holes through the 5mm bumper.

I prefer to use soldered connectors rather than crimp type but they will do the job if its all you have.
Make sure your earths are good. Earth each light separately.
Use smallest fuse that will carry the current you need.
Use the heaviest cable you have and you wont have any probs.

and remember to turn it off when you take the keys out.

I would have put the power to the switch on the AUX circuit myself but thats just me

iannotts said:

and remember to turn it off when you take the keys out.

I would have put the power to the switch on the AUX circuit myself but thats just me

Click to expand...

me too.

me 3, i'd take the power for the switch from the ignition switch rather than the feed to pin 30

Hi all,

I prefer to use soldered connectors rather than crimp type but they will do the job if its all you have.

Click to expand...

Yes crimp connectors are all I have. I wouldn't mind getting some solder connectors. Would those also be the correct size pins to fit the factory installed wiring connectors?

I would have put the power to the switch on the AUX circuit myself but thats just me

Click to expand...

I agree that is a good plan but it is just a matter of where to connect the switch. I guess you could connect into the AUX circuit in the fuse box but its just getting the wire there (neatly).

Is there anywhere better to pick up an ingition switched circuit? The vehicle is a basic trim TD5 hard top.

I also need to find somewhere to locate the switch as all the blank plates under the dash board have been used. I was looking at drilling a hole to fit a switch on the underside of the dash board beside the existing switches but there is not enough depth behind to take the switch assembly complete with wires.

fag lighter socket??

thought fag lighter was constant live Pikey?

pends what vehicle you're in, my 110's constant but the racing nissan's is switched. No idea in a Td5

iannotts said:

thought fag lighter was constant live Pikey?

Click to expand...

Some is and some int I never been in a td5 so weren't sure. But it isn't difficult to find a ignition live in a deepender is it? I take it the fuse box is in the same place. If so just remove cover and use a tester to see whats live and whats not and then turn ignition on and see if any of the not lives have become live? easy peasy really.

True enough, why not got behind the steering colum shroud?

Have the 110 outside now. Having a look at whats what. Will see where the wiring to the fuse box comes in from and see if I can push a wire through. Otherwise will look at the steering column. The truck is super tidy inside so I don't think loose surface cabling is the order of the day.

Got to get into the battery box first, there is a rubber lining over all the access panels which I need to get past first (there are some slits cut to lift the edge where the cover catch is but not much else seems to simply pull up to get into it. May have to cut it further?)

Did you know you can solder the crimp connectors shown in your picture.
I do at times, two ways to do it.
1..............Push more wire than need past the crimping section, crimp it down then solder the extra wire on the triminal
2..............Cut off the blue/red plastic bit then solder.

Any way soldering has two schools of throught now in the motor trade, most of the German car companys now ban it and will void the electrical warrenty if found.

why? Surely it provides a much more reliable connection?

It is claimed that the solder has gas trapped within it, that starts corrosion also the resistance has been changed. Another part of the arguments is that it is now a joint which has no flex in it and that the joint can now sear.
I understand that in the aircraft world joints are crimped for that reason. Any way in BMW/Audi/VW its banned.

It could also be because most people cannot solder, too much heat or to little heat both of which will give bad joints.
Me i do both depending on what i am doing.

boydy1989 said:

why? Surely it provides a much more reliable connection?

Click to expand...

Have you ever heard of 'Dry Joints' ?

Or ever had to try and trace one

Less likely to suffer corrosion in the joint if done properly. There are good and bsd points about both methods. The critical thing on both systems is that the joint must be made properly.

Well I can solder with difficulty and my soldering isn't fantastic (it all just keeps sticking to the iron) so I would not be one to know when I am using to much or too little heat and so I recon crimps are my best hope of making a good connection.

I am using a ratchet crimp tool so my connections should be OK. I always make sure that I have undamaged and clean bare cable for the length of the terminals contact surface with some twists to stop it all coming apart when putting the terminal on. And once made give it a gentle pull to check it is properly attached.

As for the task in hand, cable run from the battery to the relay is done. The lights haven't been fitted yet but that gives me time to work out a cable run avoiding as much as possible.

The lights are going on the front bumper so thinking of dropping the cable from the engine bay to the chassis and running in conduit to the bumper as opposed to trying to feed cable unsightly around the radiator and through the front grill.

Clearly I will keep the cable from being on the bottom of the chassis although the vehicle is many road going anyway.

Is it also exceptable to earth the lights using some of the existing chassis bolts say on the inside of the bolts where a steering guard is mounted? Again they will be kept out of harms way as much as possible. From the chassis I was going to run the cables along the inside of the bumper using adhesive pads and cable ties (the lights are going each end).