Negative switch problem, slightly different from normal.

Hi all, trying to install a foglight and struggling with the negative switching headlamps.
It must turn on with the headlights and not sidelights, but not be able to be turned on with the sidelights.
I'm stumped.

I've tried so many permutations.
I have thee cables going into the headlight bulb.
All are live.
One goes dead with the headlights on
One goes dead with main beam on
One is always live

The problem is I need to pick up the feed from the headlight, but I'm honestly struggling to understand how it works.

I have tried a relay with a number of different permutations.
I know light bars get fitted often, only to work with main beam, but I've also read a lot of information, including multiple schematic diagrams, but I can't make any headway.
Any suggestions?

First off, if they are foglights intended for use in conditions of reduced visibility, they are wired to work with the sidelights, as the point of foglights is to drive on them in fog with the headlights off.
They have to be a pair, angled down 3% with a 75kg driver, within 400mm of the outer edges of the vehicle, and below 1200mm (they are substituting for the obligatory headlights in fog)
(RVLR 1989 section 20 & schedule 6)

If they are driving lights to supplement main beam, they can only come on with main beam- (RVLR 1989 schedule 5)


Which of course, complicates the wiring!

The side lights use a switched live.
The main beams use a switched earth.

So if you are going for foglights (sidelight switched) your relay coil goes between earth and the red/yellow wire (with your switch in series)
For spot/driving lights between live and the red wire from the column switch

Like this (I assume you can wire the lights to the relay + fused power)
Note, if you have an illuminated switch with a third terminal for the internal bulb the 3rd terminal has to go to live for the spotlights, and earth for the fog light.
Or just wire a warning lamp where I've shown the bulb inside the switch.

If the switches have LEDs in them not bulbs, I'd have to think about it, but I suspect the spot light one won't work.


 






 

What Jimny ( model/ year) do you have? The wiring changes between negative switching and positive switching depending on the model you have

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You are aware of the possibilty that your jimny has the original Wiring for fog lights even though the lights and switch it is not delivered with the car?
Mine 2005 had all the wiring done so all I needed was the switch and the lights. plug and play.
however my fog lights with the original wiring can be switched on together with the low beam. (or just parking lights.) But it has been ok with the MOT (Norway) but still is illegal to use here in most cases. only daytime fog/snow possibly, and never with the low beam on.

yakuza wrote:

You are aware of the possibilty that your jimny has the original Wiring for fog lights even though the lights and switch it is not delivered with the car?
Mine 2005 had all the wiring done so all I needed was the switch and the lights. plug and play.
however my fog lights with the original wiring can be switched on together with the low beam. (or just parking lights.) But it has been ok with the MOT (Norway) but still is illegal to use here in most cases. only daytime fog/snow possibly, and never with the low beam on.
 

Which is how it is in the UK.
Foglights can be used instead of the dipped headlights in conditions of reduced visibility (<100m), provided they are fitted to meet the requirements of RVLR 1989 schedule 6, so they are wired to come on with the sidelights.

Driving lamps are supplemental to the main beams so they have to be wired to extinguish when the headlights are dipped.

Firstly, thanks for all your replies, very detailed!

Just to clear a couple of things up.
It's a rear fog light, so the regulations are different in as much as it has to not be able to be activated on sidelights.
It can only be activated with dipped beam, main beam or front fog. They're very strict with that.
(I think it's odd, because the front fog can be on with sidelights, so it seems to contradict itself)
It has to have a switch with a visible tell tale light on it too.

I struggled with his because I looked at so many different wiring diagrams, and all were slightly different.
Mostly they were concerned with light bars, driving lamps etc., working off main beam.
I tried some permutations, mostly they all had an earth coming from the relay, which was causing my headache.
I spent literally all day trying different things and could not get it to work.

I eventually, gave up, went inside, sat and thought it through, and (rightly or wrongly) I worked out a solution.
It works but I'm not sure if it's the correct way to do it.
I ran the trigger for the relay to live, and to the headlight wire which was live, but earthed when it was activated.
And the other live to a switch on the dash - which when the relay was triggered by the headlamps, the fog light turns on.
Like this:

My only issue with this now is that everything works, the fog light only activates with the headlights, not the sidelights.
However, the switch on the dash will illuminate when it is switched on, irrespective of the headlights being on or off.

Is there anything glaringly wrong with how I've done it, and is there a solution for the switch.

I did think I could possibly try putting the switch on the headlight circuit not the fog light circuit, and instead of running the third terminal to earth, running it to a live - so when the headlamp was turned on, and became earth, it would activate the switch?
 

mlines wrote:

What Jimny ( model/ year) do you have? 

I have to ask why the original one is not sufficient? 

So What jimny and year model and market is this? 
Doesn't all have the rear fog light?

does vary if it is down in the rear bumper lamps or up in the main rear lamp assembly between markets and year, but they all have them here in Norway.

I can't see your diagram, you can attach an image into a reply on here, but they come out small.

Anyway, if you have a 3 terminal switch with a telltale bulb, look at what I sketched, the tell tale bulb connects internally to one switch blade which goes to the load, and there is an odd terminal for the other end of the bulb (different colour or size) which either goes to earth (positive switching) or live (negative switching)

If the tell tale bulb is on all the time the circuit is "live"  it sounds like you have the switch blades wired backwards, swap the feed and load terminals over.


(normally the switch is put in the wiring to the relay coil like I did it, then you wire a fused live directly to the lamps through the relay contacts, but for a 21W bulb it makes no difference where the switch is)


Oh, and you are only allowed to use the rear fog in conditions of reduced visibility, when you are required to have either dipped headlights or front fogs on (or both if you really want...) so wiring it off a headlight or front fog feed is correct.