Light switch relay sticky

[Colin McA]

The topic does come up fairly regularly and I am wanting to fit some myself an am not sure whether to go for a single relay near the switch or After the headlamp and dip switches.

Looking for a couple of views on this and maybe get it made a sticky??

Colin

[johnwp5bcoupe]

Hi Colin as the switch is a single pole 2 way you would need a single pole relay as either/or has volts on it you will have to choose which has the volts on when energised HL or Dipped or use two relays the wiring will take the current IMHO so it just after the switch or just before the HL will make no difference!

[Phil Nottingham]

I have just fitted the one HD minature relay behind the switch - it would only need the 2 if you are running really high watts bulbs

[Colin McA]

I am running Halogen but just the bog standard type.

I am not concerned with the wiring just the switch which is already suspect.

In-fact I have my speedo out at the moment and when the lights are on the main beam light is getting some voltage as it glows, you wouldn't see this when fitted with the blue lense. Certainly made me concerned.

So the options are

A) single relay after the light switch.
B) two relays after the dip switch and the flasher
C) three relays as B plus one side lights.

A) means sidelights are still through the dash switch. and full current goes through the flasher. column and dip switches.

B) Side lights still through the dash switch. but relays after the column and dip means that they carry low current.

C) as per option B and sidelights load goes through a relay energised from dash switch

Ideally I think I will go for option B with potential to put a relay on the side lights.

Colin

[johnwp5bcoupe]

Colin I wouldn't worry about the side lights in respect of fitting a relay the current is well within the switch capabilities, if you are happy with the wiring just use a relay to protect the switch for the headlights, if you really want to go for it fit one to protect the flasher switch

[Colin McA]

I will have a look at how handy the connectors are for getting at.

The switch is the main concern so Might just fit the one there. It is handy for taking a feed from the switch and shunt.

I like to keep the wiring tidy.

Colin

[Colin McA]

I have now wired up the relay.

I have went for a single relay after the dash switch but before the others.

Below is a basic diagram showing the relay. It should make sense if you compare it to the full wiring diagrams. I have taken the feed from a spare tag on the Ammeter shunt.

Colin

[mcgill]

Is there a wiring diagram for the best relay feeds,and nice place to put them out the way,?? anyone has ,be very handy as putting car back together ..........its finally painted in colour.......but i miss the old metal stabizer colour in a weired way ,i shouldve just laquered it...

[Baldrick]

I fitted relays to my Defender. The main reason is that the voltage drop through the standard wiring and switch means only 11.? Volts at the bulbs as opposed to the 14.4 that will be available in the system.
There is a big difference between the light that 14.4 gives out compared to 11.4 on the same bulb

[Colin McA]

This is the original diagram from the post.

[Allan NZ P5b]

I am going to tackle this another way as I have plenty of relays and its a saloon with separate fused circuits for each side main and dip.
I am planning on placing the relays close to the Headlamp bowls, not sure whether inside the guards or inside engine compartment yet. 4 relays one for each main and dip. and use the original circuit to power the relays,
I understand this will protect all the switches and wiring.
My Questions are

1. where should I take the new feed from for the headlamps?
2. easiest location and route to run to either left or right side?
3. do I run 2 feeds one for each side or one, and cross over behind grill somewhere?
4. What gauge wire do you suggest, what colour is most correct?
5. What should I do about fusing the feed? inline? what amps

Bulbs are halogen 12v XD1260/55UP H4 Halogen Ultra Plus Bulb - 12 Volt
Hella product page

Cheers in advance.
 

[johnwp5bcoupe]

Sound as though you have the solution I would also go after the column switch.
12v pickup Colin has a good solution wiring route is a personal thing as is the colour, follow existing colours to save confusion? fuse wise each lamp will draw 5/4.6 amps so you should use 10amp minimum cable with slow blow 5amp fuse or 8 amp standard using a 5amp standard will work but may get warm and eventually fail? if you are using 2 relays (per side?)that is better all round as all the switching is protected inc flash.

[Allan NZ P5b]

I have completed the Mods as per diagram attached have had to feed the power from an alternative source to the one I wanted to use (the spare terminal on ammeter Shunt) as I couldn't locate a female spade connector of the right size 1/2 inch i think.

Can anyone point me at a supplier of these anywhere. I don't mind purchasing off internet I can't find a supplier.



PDF of the wiring


Headlights are running well via an alternative feed and are superb, but would like to tidy up this wiring feed Thanks 

[djm16]

I would recommend not running your new power feed from the ammeter. It defeats part of the object, which is to bypass sources of resistance.

If I were doings this, I would run a single cable from the live feed to the starter solenoid to the L headlamp relay and then on to the R.

How to choose the current rating?
The current through each filament is around 5A. Since it is possible to have dipped and full beam on simultaneously when you flash your headlights (in modern cars, but YMMV) you may need to 20A cable to cope with the load.

[johnwp5bcoupe]

If you mean by saying the "Ammeter Shunt" the connector block on the battery side of the Ammeter where all the brown wires are that is fine to connect there, as djm16 says a 20amp feed would be a good idea ;)Spade terminals are easily found here all sizes

Vehicle Wiring Products

[Allan NZ P5b]

Thanks John, yes I do mean the ammeter shunt where all the brown cables are. the spades on there are bigger than the 9.5mm 

on this page, more like 1/2 an inch. cant get anything in to measure and don't have a spare off the car.

If someone has one off they could measure that would be good

Vehicle Wiring Products on this page biggest was a 9.5mm and I have bought those but it is too small to fit.

Regards and thanks

[johnwp5bcoupe]

Apr 11, 2014 8:45:14 GMT Allan NZ P5b said:

Thanks John, yes I do mean the ammeter shunt where all the brown cables are. the spades on there are bigger than the 9.5mm 

on this page, more like 1/2 an inch. cant get anything in to measure and don't have a spare off the car.

If someone has one off they could measure that would be good

Vehicle Wiring Products on this page biggest was a 9.5mm and I have bought those but it is too small to fit.

Regards and thanks

Hi Alan yes they are 1/2"! I have rung round a few wiring loom makers and there is a huge shortage of 1/2" spades I was asked if I find any can they have the suppliers details!
Anyway if you only want one or two I have some secondhand ones which are reusable if they will do PM me your details just postage charge

[johnwp5bcoupe]

It's in the Post Alan