Relay function in lighting circuit?

[Cuppa]

As part of my current quest to do something about the woeful headlights on my car, I also want to try to understand what the setup I have is. Elsewhere I was asked whether the GU has light switching at the stalk as standard. I couldn't answer that 'cos I don't know.

Having looked at the wiring from the rear of a headlamp back. First I have a piggy back connector which crosses to the two IPF driving lights fitted by Telstra & following the wires from this in the opposite direction, through the jungle of Telstra added wires, (most of which I have no idea what they are/were for, nor whether they could be safely removed) the headlight twin wire leads to a relay as below. This is six pin relay, with Nissan marked on it. A heavier wire coming from it leads to a positive terminal at the end of the factory fuse block via a 30 amp inline fuse which I didn't know I had until today.
I'm guessing that this relay, bolted to the driver side wall of the engine bay approx 200mm in front of the firewall, probably controls both on/off & high/dipped beam at the same time somehow. Can't quite get my head around that. Could be wrong. But if that is what it does then presumably, being a Nissan part, the switching was never at the stalk on this car. Does that make sense or am I mistaken?

Does this diagram mean 2 things are switched simultaneously?



Power is supplied from this connection on the end of the factory fuse tray, presumably just a handy alternative to the battery's positive terminal?

[Cuppa]

A bit more. Holding the relay I can feel & hear it click, not when I turn on the lights, but when I use the dip switch. So I’m now guessing it switches hi/Lo beam separately but simultaneously for right & left headlights, so presumably they are on separate circuits? Someone suggested this may be an ADR requirement, but it’s all guesswork. At times like this I really miss ‘Yendor’! I’ve been going through the w/shop manuals, but I can never work out which one pertains to my model, & trying to make sense of the wiring diagrams has my head in a spin & I have still not found anything which might relate to this relay.

[mudnut]

Yeah, Cuppa, the driving lights are supposed to turn off when you switch the headlights to low beam.

[Cuppa]

Yeah, Cuppa, the driving lights are supposed to turn off when you switch the headlights to low beam.

Hiya, I think you may have got me wrong. I know what you said is correct, but the relay was operating the headlights. The driving lights were not switched on. The point I am trying to clarify is whether a stock Patrol uses a relay to switch between high & low beam (without any driving lights fitted) or whether this switching occurs, as I have been informed , at the switch on the steering column. I think there are 4 possibilities - either 1. what I have been told is correct, but Nissan changed how they switched hi/low beam on my car - the relay is clearly a Nissan item, .... or 2. What I have been told is incorrect, & Patrols utilise a relay to switch high/low beams . or 3. When Telstra added the IPF driving lights they added a single relay to switch the headlights & used a genuine Nissan double pole relay from some other application or 4. I am wrong about the function of this relay in in my car.

The only certainty is that the relay can be felt & heard to click when I change from low to high beam or vice versa.

I could be quite wrong, but currently I think this is probably what I have, or close to it. (Crap drawing, but hopefully self explanatory). Having drawn it, I feel it is unlikely to be a factory setup, just that the use of a genuine Nissan Double pole relay has confused the issue.

screenshot_372.png

[mudnut]

The wiring diagram I have seen for a GU has no relays. If Telstra knew this, they may have ordered the dealers to fit one on each vehicle before delivery. I fitted Two relays on my Q.
One for High beam and one for low.

[Cuppa]

The wiring diagram I have seen for a GU has no relays. If Telstra knew this, they may have ordered the dealers to fit one on each vehicle before delivery. I fitted Two relays on my Q.
One for High beam and one for low.

That is a possibility I am entertaining, but remain puzzled as to why a double pole relay & not something like used on the various aftermarket looms. I suppose it still gives me some nagging doubts. 1. Is there a specific need for this type of relay & if so how should I go about adding on an aftermarket loom, or can it simply be dispensed with.The GU wiring diagrams I've seen have a whole lot of switching without, as you note a relay, & I wonder if somehow that has it's own special requirements - hence the double pole relay. And if I retain the relay, I'll have to suss out how to fit an aftermarket loom or a home made one which incorporates it. The diagram I've drawn is a guess as to how the relay is used. I expect there may be other possibilites for the 6 wires attached to it.

[mudnut]

The contacts on the light switch take the full current and burn out prematurely. The relay coils only take a fraction of that current to switch the lights on. The length of cable from the battery to the lights can also be reduced, thus reducing voltage drop.

[dads tractor]

Cuppa we can rule out the Telstra extra because my 1999 st 4.2t has the same setup. Not X Telstra

[the evil twin]

Hiya Cuppa,

I don't think your drawing is 100% correct but close and I also reckon your lo beam is 100% factory IE all current thru the stalk with no relay.

IMHO I reckon you will find that the double pole relay will be de energised (contacts open) on low beam and energised (contacts closed) by hi beam selection to reduce the extra amperage of the driving lights flowing thru the stalk switch.

It is probably like that from new because Nissan won't see any need to mod the lo beam side from the shitty factory set up of no relay at all.
If I am looking at the correct wire in the piccy that type of fuse holder and the piggy back plug says to me that the mod was done after Japan but before/on Delivery hence the Nissan relay.

The piggy back is normally used to sense hi beam so you don't have to cut into existing wiring and also supply additional power to the Driving Lights (one pole for each light) but without testing your plugs I can't guarantee that is how yours is done.

[Cuppa]

Some Progress.

I have ascertained that the double pole relay only relates to the IPF driving lights. With the relay disabled the headlights can still be switched on & changed between hi & lo beam.

It appears to be triggered by a red wire with black trace which comes through the firewall which is also connected to the driver side headlight high beam pin.

The diagram I had hoped to draw is in the too hard basket. Too many wires I can't access.

However it does appear that the headlights themselves are still operated from the original switching at the stalk, & the red/black wire is consistent with colour of the high beam wire on the driver side in the factory wiring diagram.

The wiring to the IPF driving lights appears rasonably substantial but some of the factory wiring is very thin.

There are far too many piggy back connections in the loom, all of which had oxidised pins which I cleaned with a light emery buff (I know this is not the best way to do it, but it's all I had & besides this loom is going to be replaced soon).

Overall, I think I have a basic understanding of the operation, but there does seem to be more complexity than I would think necessary. For this reason I think I am going to buy a ready made replacement loom to power the headlights directly from the battery. Looking at the Pirahna super loom I believe I can fit it & utilise the 'driving light trigger' wire which is part of it to replace the red/black connection to the double pole relay for the IPF's.

I believe too that the wiring loom which is supplied with the Stedi Light bar should be able to have it's relay triggered either from an extension of the same trigger wire used to operate the existing relay, or from the power supply to the existing IPF driving lights (I imagine the former might be better). This way I keep the circuits for the IPF's & Stedi separate, but still switch on with the single switch I currently have for the IPF's