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Good point - I'll need to check and see how I did the headlamp relays; I can't find the drawings.  Those relays are sitting behind the ignition coil on the RH inner wing.  I do remember that I did use bullet connectors into the original connections and seem to recall that where there was only a single bullet I changed it to a twin-barrel, double bullet connector.  I plan to use the same strategy again, and have tripple barrel connectors on hand if necessary. 

Everything I've done is 100% reversible in that the original loom is intact and never been cut; it makes for a few meters of extra wire back and forth from switches/relays to the original connectors, but if I'd ever needed to undo something, the loom's integrety hasn't been compromised.

So about the safety aspect of switching between the two circuits via the ground wires; no dangers?  I imagine that only when the battery (-) is disconnected for vehicle repairs then I should also disconnect the positive also? 

So, maybe this is minutiae but you are also powering the headlamps via relays. I would trigger them all via the original wiring so that if there was an issue with the low beam relay and it did not turn the lights on, the signal would still go to the fog lamps relay. The original loom can easily power two relays.

Another thing to consider is that I still power the running lamps via the original wiring and switch.

Ok - Added the rear fog lamp.

Just to be certain, are there any risks or liabilities in using the switch on the ground wire?

Edited to exchange attached image

Hi mur,

Yes I do - I knew I forgot something.  Give me a minute and I'll incorporate one. 

Excellent. Now, don't you need a rear fog lamp where you live?

I put pen to paper and have attemted to draw what mur suggests, switching the ground to the relays. 

What do y'all think?

I think this is what was meant -

This would be much easier if you had a DPST or DPDT switch so that I could isolate the circuits. But i'm concocting something in my head that I'll try to get on paper tonight if I can. 

Here's an issue to consider. If you have covers on the driving lamps you'll have to take them off to even use the high beams if you wire the relay to the high beam circuit. You won't use the driving lamps very often but there will be many times you'll want the high beams. This is my experience which caused me to re-wire my spots onto a separate switch.

You want the driving lights to be switched independently from the high beams. They are actually not legal on the highway, despite the perceptions of the mall cruising 4X4 world, therefore they need their own relay.

give the driving lights their own +12V trigger from the original wire harness high beam wire, and as I said before switch the ground going to the relay. I don't recall if 85 or 86 is +or- and some folks say it can be either.

like this, the driving lights are only on when you have the high beams on and the driving lights are switched on. With a warning lamp inside the car, that lamp also lights up when it gets a ground.

if you have a six connector three position toggle switch, one side can operate the high beams and the other can do your fog lamps. Again, the fog lamps relay can be set so that they only operate with the headlamps if you choose.

Many cars have more complex relays so that one unit can do both high and low beams, but these are expensive. For half of the cost, the weatherproof Hella units can be had along with the sealed base and wiring.

Cool - I'll just keep it simple and simply wait for the parts to arrive.  As you've all implied, there's no need to re-invent the wheel.  I like to be prepared, so I'll make a sketch before I get started. 

It's nice to see that this place can still function, thank you all for all your help. 

You'll want the driving lights to be on every time you use the high beams anyway, so it is convenient to combine their function through the already existing high-beam switch (as Ian pointed out, the switch won't see any additional current so it will be fine).

If you do it this way, then there is only the one additional relay and switch needed, for the fog lights.

Norm

Hi jeg, I would NEVER call myself an electrician.. but the physics is not too complex...

It doesn't matter whether from an electricty flow point of view whether you switch the power or earth.  But it has to be safer to switch the power.... (IMHO

I tried to find a double switch out in the shed but the only ones I could find are in the car - and I didn't feel like standing on my head so soon after dinner so I couldn't find out whether the double switches have more than one power input....

As well as being a legal requirement, switching the driving lights through the dipswitch is a safety item.  If you're bombing down a country road with everything lit up and soemome comes around the corner towards you, a single stab on the dipswitch turns off the spots and highbeam; once they're passed a single action brings all the light back....

Cheers, Ian

Cheers, Ian, yes, I understand that the earth is common, and it would be simple by using 2 relays and 2 switches.  I've resolved myself to the fact that 2 relays are going to be used - heck, they're included in the kit.  So are the switches for that matter, but I'd kinda like to use the single pole double throw switch if I can.

But am perplexed by mur's notion of using the ground to the relay via the switch.  He's an electrician, so I'd like to hear more about what he's thinking.

I'm quoting jegs post because I've found that answers may not directly follow questions (due to time delays??) so you need to make it obvious which question your post is trying to answer......

Earths are just that - they're all common.  You don't need to connect them.... the Laws of Physics dictate that they are all the same point electrically  (unless of course they are insulated from each other by something like rubber engine mounts..... hence the engine to body earth strap(s).  ower flows throught the live wire so its the only one that needs to connect A to B....

And, no, if you use relays, then the only power that flows through the switch is that required to switch the relay.  As MMouse pointed out earlier, this only fractions of an amp...

On further reflection I think my comment re using the single double throw switch was incorrect.  I was ignoring the extra complication that requires the drivers to ONLY be on with the headlights on AND switched to high beam.  You can (I do) power the driving light switch from the dipswitch high beam.  However, this would preclude use of the same switch for the fogs because it would not be powered on low beam.

Noting that you already have a fog switch I would just run a powered line from here to the (front) fog relay. I know that means two switches ... but you already have one...

Cheers, Ian

Sure would be a lot simpler to just use 2 switches and 2 relays...

Ok, so I can use 2 relays, but I'd really like to use the single pole double throw switch.  This will take a bit of figuring out, as the center 'A2' connection needs to be 'common', for example, the ground.  And, the switch would toggle between 'A1' foglamp/low-beam ground and 'A3' driving lamp/high-beam ground.  I imagine that's why mur gave the clue as to using the ground wire to the relays from the switch. 

But, that got me thinking - isn't there going to be a lot of current flowing through the switch? 

In the standard single-pole single throw switch setup, the relays get the current (#30) from the battery cable/starter solenoid and is grounded (#85) directly to bodyshell, then the outgoing accessory + (#87), then it's 'input' switchable from the headlamp circuit (#86) are low-current. 

Here's what I think mur inferred:

If then the ground to each relay (#85) comes from the switch's 'A1' or 'A3' terminal, with the central 'A2' grounded to bodyshell or B-, then (#30) still gets B+, (#87) still 'feeds' the accessory lamps and the headlamp circuit (high/low beam) still connect to (#86) but are unswitched - (#86) is spliced directly into the headlamp circuits (the blue/red and blue/white wires). 

But, isn't this giving too much current to the switch? 

Sure wish I could sleep...

Hi jeg.. I think I got lost too..  however here's a couple of observations based on my install..

You will need two relays; the relays provide high power to the lights when switched. While some relays have multiple outputs the only ones I've seen have a single input switch (ie switch on = all terminals live).

You will want each light set to operate exclusively (ie fogs on = drivers off).  Additionally you will probably want the drivers to only come on with high beam (a legal requirement where I live).  Fogs can operate independantly of the headlights.

Your single on/off/on switch can handle both systems - and as it only switches the relay, will not need to handle high power.   I would (and do) drive the lights from the starter solenoid under the bonnet rather than run separate power lines back to the battery.

I run a wire from the live side of the dip switch to the driving light switch to the driving light relay switch terminal.  Power (18A=200w) flows through heavy duty cabling from the starter solenoid through the relays to the lights.  (I use a second relay controlled by the normal headlight switch to drive the headlights which also have 100w bulbs).

You could then use the other side of your auxilliary switch to switch the fog relay.  Just run piggy back lines to the indicator lamps from the respective switch terminals.  The switch is only handling low power (only switches the relay) so the indicator piggy backs shouldn't be an issue...

Cheers, Ian

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Mur, can you draw a diagram?  I'd assume that A1 and A3 are the ground wires to the 2 relays, what goes on the switches 'center' pole? 

I'm afraid I'm getting too tired right now, it's 0500 and I haven't been to bed yet.  I'll need to pick this up in the AM, ok?

Edit:  Might have had an ABBA moment, "AHA!"  The switch is grounded at the center A2 pole, A1 & A3 get connected to relay pin 85 (if using 2 relays).  I can't imagine trying to get it to work with only 1 relay and the single pole switch, though. 

The small dash lamps would piggy-back their 12V+ from a different source altogether, break ground to turn off, interesting. 

Yes - Position 'A' for front and rear fogs, osition 'C' for driving lights; each with their respective red or blue piggy-backed dash indicator lamp.  osition 'B'is off.

Sorry, but I just can't see how the one single-pole switch could operate both relays, maybe you can walk me through it.  Here's the switch brochure APEM Brochure (page 3). 

You can switch the relay on by running the ground to the relay via the switch, and the ground can also ground a warning lamp.

A dual pole switch can run some sophisticated things if you really put your mind to it.

Dual pole, dual throw, more options, however it is OK to just be simple.

Ah. ok. That's the part I was missing. The rear fog will be on with the front fogs, but not with the driving lamps, correct? So basically position "A" will be low beams on, fogs on, rear fog on. Position "C" will be high beams on, driving lamps on, and no rear fog? All positions whether driving lamp, fogs, or rear fog will have the dash indicator? And I'm assuming the rear fog is already on its own relay.