Best way to power driving lights?

[240ZMan]

73 240Z:

I just got the driving lights working for the first time. They are powered directly from the battery (separate in-line fuse) and activited by a relay. I noticed that when they are on, the ammeter shows a constant state of charging that returns to neutral as soon as I turn them off. This makes sense as the ammeter doesn't know the difference between current charging the battery and current flowing into the lights.

So my question is two fold:

- anyone run like this for a long period to have some experience that this won't bother the proper charging of the battery?

- if I decide to rewire from the battery to some other point "before the ammeter", where should that be? I'm thinking that the big red main power feed into the fuse box would be good, and I'd move the inline fuse close to it. But is there a better place?

[Bambikiller240]

Are you aware that he 240Z's had wiring built into the wiring loom for driving lights? Up front, near the horns, feel around on the wiring loom for a bulge near each horn. That is the connectors for driving lights. It has been folded back and wrapped in tape from the factory.

***Now I'm no electrical wiz, and I don't know what amperage you would draw with the lights you bought. Also, I don't remember where the other end of those wires ends up, so you'd have to look at a schematic and look around under the dash (probably).

Anyway, just thought I mention this.

[240ZX]

240ZMan,

Your electrical hook-up is the way it should be done. This is the recommended method and is usually recommended by the driving light manufactures. The load you see on your amp meter is normal.

[Daniel]

The power source is the same(battery)wherever you hook them up.Odds are you see the same thing when your turn signals flash or you normal head lights on.The battery doesn't know or care.The voltage reg.senses that the battery requires a charge and allows the alt. to provide that charge.Once again they don't know or care where the load is,it just knows it needs to provide provide power to maintain the proper level the volt reg. wants before it shuts off the path to the alt. Think about if you move a lamp to a different receptacle in your house.It doesn't change the meter as the power source is still the same. I'm Curious,Did you install the relay on the pos. or neg. side?

[EScanlon]

I currently have my driving lights hooked up through the car's wiring.

Some notes: I am only using low wattage driving lights, (think about 40 ? watts.) this is because I'm specifically avoiding using any bulbs with a power rating greater than the headlights. Remember, today's 100+ watt halogen's were NOT around when the car came out.

If you do plan on using the higher wattage lights, then definitely power from the battery and use a relay.

The inside end of the fog lights should be right below the radio and behind the fuse box. If I recall it's a Green White wire with a black. Note that you only need an SPST switch to close and turn on the light circuit.

Enrique

[240ZMan]

Originally posted by Daniel

The power source is the same(battery)wherever you hook them up.Odds are you see the same thing when your turn signals flash or you normal head lights on.The battery doesn't know or care.The voltage reg.senses that the battery requires a charge and allows the alt. to provide that charge.Once again they don't know or care where the load is,it just knows it needs to provide provide power to maintain the proper level the volt reg. wants before it shuts off the path to the alt. Think about if you move a lamp to a different receptacle in your house.It doesn't change the meter as the power source is still the same. I'm Curious,Did you install the relay on the pos. or neg. side?

Thanks Daniel, I share your view of how the system works. My question if others had some experience with this configuration (connected straight to the battery) was just trying to be sure that "theory" and "practice" would be in synch:classic:

BTW, I put the relay on the positive side. I actually took the power to enable the relay off of the light switch under the steering wheel through another under-dash switch so that I don't have to remember to turn off the driving lights separately.

[billcapp]

Unless you are using more than 55W lights you shouldn't see very much indication on the ammeter. You might want to check your alternator brushes. I use 55W bulbs for fog lamps, have a newly rebuilt alternator and don't see but a very slight rise in current drain on the ammeter (less than 1/32 inch movement) at idle.

[Daniel]

Good idea with having the relay in series with the main lights.The most correct way would be to have the load of the relay on the neg.side.Fuse the pos.Let me explain better.The way the relay is triggered is fine.The part of the relay that the lights run thru should be on the neg. That will extend the life of those contacts.Allow me to make you go hmmmmm.The brake light switch on the car switches to ground. The horn goes to ground. The points are on the - ground side of the coil. The door switches switch to ground.The fuel,temp and oil pressure switch to ground.The load is between the pos. and the device.The stress is less on the other(neg side)of the device.HMMM-huh?

[LanceM]

Well Daniel I'd have to disagree on several points and I will explain, not bashing just my opinion.

1. The approved method of power switching is always switch the hot or + side. Otherwise there is always power at the socket, with higher voltages this could be dangerous because with the switch off you would believe the socket to be dead or unhooked, when if you switch the low or - side the socket would be hot looking for a ground, which you could supply with your body. Often times too auto lights in particular often use the chassie as ground so it would be difficault if not impossible to switch the low side. It is also best to switch the hot side as close as possible to the power source, this way as much of the circut as is possible is unpowered when it is switched off.

2. Where the relay is in the circut + or - will not extend the life of the contacts, ohm's law states I=I/R, this is the same in any point of a circut, so whether you switch before or after a load the contacts will see the same amount of current surge at closure. The best way to extend relay life in a high current (anything over say 2-3 amps) is to buy a relay with contacts over rated by 2-300 %, once you get to around 10 amps the best way to go is with a continuous duty solinoid, much like what is used on a starter. They can handle several hundred amps of surge current and pass 40 - 60 amps all day everyday for almost forever and are rather inexpencive usually around $10.

3. Brake lights switch to ground.... I think you will find that the brake pedal switch switches 12V, all of the rear tail lamps use a common black wire ground.

One thing that I really agree with is fuseing the positive side. Always fuse as close as possible to the power source and remember the fuse is there to protect the wiring, not the device. Don't over fuse, 10A fuse on 18 gauge wire will make for a smoked wire, so for heavy current devices run the heaviest wire you can for the device you are going to run and fuse the circut to protect the wire if the device should fail.

[Daniel]

Lance, Boy I'm glad someone went whaaa...You are indeed correct on your switching ..if source was standard AC or DC. Cars are different.I presented your same viewpoint once upon a time to a ex- navy sub engineer and a current 25 year gm certified tech.I lost. Agreed the potiental for 12v is there ,but you will not be the path to the neg or the battery.Its not like your house.Check you wiring diag. you will see the brake does have the common ground you refer to but the switch goes to ground.As far Ohms law .The theory is correct again.The reality is not.In the electrical code you are allowed and is common what is called a "reduced neutral".If I run say 3 #10's (30a each) I can use one #10 as a return.Thats why if your house has a 200amp meter you have two 2/0 hots and one 1/0 return or neutral as it is called.Sorry to rattle quick but these post timeout so fast. I enjoy the discussion. Daniel

[ozlime240z]

Originally posted by 240ZMan

73 240Z:

- if I decide to rewire from the battery to some other point "before the ammeter", where should that be? I'm thinking that the big red main power feed into the fuse box would be good, and I'd move the inline fuse close to it. But is there a better place?

I run all my After Market Under Bonnet Accessories (Air Con, H4 Headlights) off the positive connection on the Alternator. That way the Ammeter stays true to what is actually happening. As an added bonus, when the Car is running this is the Highest Voltage point on the car, as this is where power is being generated and has not run through any wires. About +14V. Makes the H4's work well

The way the ammeter works is it detects current flow in a particular direction. On one side of the Ammeter is the battery, on the other side is everything, yes everything else, including the alternator. When the car is running the Ammeter should read close to 0 (or very slight positive) as the Alternator should be 'running' the car. If the battery is flat the Ammeter will sit continually hi on the + side as the alternator is trying to charge the battery, or if the Alternator fails the Ammeter will sit continually low on the - (negative) side as the car is running primariliy off the battery.

It is definitely best to run all devices off the "Car" side of the Ammeter not the Battery Side. That way your ammeter will tell you if there is a problem, which is why it's there.

My recommendation is to run all under bonnet after market electricals off the Positive of the alternator and fuse at that point.

I will post some photos of my set-up if anyone is interested.

Seeyas

OzLime240Z

[LanceM]

Daniel,

Ok, I checked

My wiring diagram shows 12V + being switched for the brake lites, and I took a test light and checked, 12V at the switch all the time, press the brake pedal and 12V on the other side of the switch. I was pretty sure before I checked as the trailer brake controller I put in my truck needs 12V from the brake switch to turn on.

I could see switching the low side if you use a common buss for power, but in either case the same amount of wire, really more if you switch the low side, is going to be used. It would make the most sence (less wire) to switch the high side using the chassie as ground where ever it is available, which is pretty much everywhere.

Oh well don't really matter, too many years working aircraft wiring I guess.