Headlight wiring

[CrashNBurn]

This question is intended more for those who have plenty of experience and knowledge in the black magic of electrical theory and wiring stuff. But really, anyone feel free to answer. The attached wiring diagram is my attempt to figure out this entire headlight relay-wiring thing. Please keep in mind, that wiring is not my forte, so I most likely put some component in the wrong place. However, that is why I'm asking you guys. Which parts are correct, and which parts need fixing...on the wiring diagram.

Now to be more specific...Are the fuses in the right position? I mean, should they be wired in before the switches, between the switches and the relays, or after the relays? Do I need that many fuses? Should each light have its own relay? I'm not aiming for absolute redundancy, but rather, a blend of simplicity and precaution for those instances that "Murphy's Law" takes effect.

Is using the main headlight switch to power the high beam/low beam switch the best setup, or are there more ideal alternatives? I know the red wire with a black stripe powers the high beams and the red wire with white stripe powers the low beams, but what about the red wire with yellow stripe and the plain red wire? In my Haynes manual, it simply has them going to the fuse block, receiving power from the positive battery terminal (or alternator when the car is running). I really cannot figure out the function of those two wires. Are they ground wires for each headlight, because as I've drawn, the headlights have no ground? Although, are the headlights self-grounded through their case? Anyways, in this circuit, what would be the function of the two wires? Thanks in advance for any help!

Jason Tripp

Headlight Wiring Diagram

[TomoHawk]

The lights have only one ground for each bulb, and the power wires are always hot, the ground leg being the switched one. Use the OEM switch to trigger the relays. I'm planning on one relay for both high beams, and one for lows, and you shouldn't need a fuse to power the relays; a very small one should do (check relay specs).

I think the last problem is to have good, clean connectors on the lamps themselves.

[wal280z]

Just off the cuff, I would think that if you supply both relays with one fused circuit, rather than two as you show, it would prevent burning out both headlamps if a relay malfunctioned (shorted in the 'on' posisition), allowing the owner to troubleshoot the cause of no headlights when a fuse blows. The way it is drawn now, however, does allow both high and low beams to be on at the same time if a relay shorts out. A single fuse circuit would allow the fuse to blow rather than both high and low beams to be on at the same time (that is, if you didn't put a 50A fuse in there).

Just my 2¢...

Wayne

[CrashNBurn]

Thomas....Wayne....thanks for you advice! Hopefully, the the updated wiring diagram I posted is correct. Is it alright to switch from the power wires and use the third wire of each headlamp as a ground? It makes sense in my head, but then again, I'm not the expert...

I'll be using 10 amp fuses, just like the factory setup. However, I'm upgrading to ATO/ATC-type fuses with a revamped fuseblock. The relays are five-pin, Bosch automotive relays with a normally-open rating of 50 amps and a normally-closed rating of 20 amps. While the now single fuse for each relay should blow first in the event of a meltdown or short, things can happen...like you said Wayne.

http://www.classiczcars.com/photopost/showphoto.php?photo=12208&size=big&sort=1&cat=500

Well, here's the link for the updated wiring diagram. I took the liberty of adding in the high and low beam headlight elements for the sake of clarity. If there are still errors, please let me know. Unfortunately, I must get my Zed running before I can upgrade the headlights. Once again, much thanks to both of you for your help. If there is any way that I can ever help, feel free to ask, although it is doubtful since I have so much to learn...

Jason

[TomoHawk]

Use all new wiring. Try to avoid the old, cruddy wires, which will make the lights just as dim as it was before you added relays. Make sure you have a proper ground connecton.

It will be tough enough having brighter lamps ifyou are still using the rusty original plug on the back of the lamps. It would be nice to put in new lamps & connectors.

[TomoHawk]

Since you brought up the topic,

Does anybody know of a GOOD source to get one of those headlights-on reminder/buzzer things? NAPA doesn't have them, and a J.C. Whitney search gives you 500 items matching 'headlight reminder.' :/

I killed my battery twice last week.

thx

[CrashNBurn]

Thanks for the advice. And yes, I will be going with new wiring and connectors. But now that I've figured out the headlight wiring, it seems that my ignition is not working, argh. As far as I can tell, continuity is great and everything "seems" to be wired correctly. But with some genious's wire hacking and such, in addition to an indecipherable wiring diagram in my Haynes manual, I'm rather stuck and confused. Bumming rides off friends gets old rather quickly, as this is supposed to be my daily driver. :dead:

Thomas, if you want a headlight alarm, the two J.C. Whitney parts that seem best suited for the job are:

SJ734756N $7.99 "beeps until you turn off lights"

SJ475974W $23.99 turn-signal-on reminder "beeps 3 or 4 times every 40 seconds & LED flashes to warn you that turn signal has been left on."

A company called Ron Francis Wiring makes replacement wiring harnesses for classic domestic cars, but also sells individuals components, such as switches, dimmers, flashers, relays, lights, etc... Some of their prices are a bit high, but the products seem rather useful, even on an old Datsun. One of their products is a turnsignal warning buzzer, part number BA-12. It sells for $29.95. You can check out the website at http://www.ronfrancis.com

If anyone reads this and would care to help with my ignition issues, please feel free to chime in. I can provide more details of what has already been replaced and the condition of the car, if needed.

Jason

[TomoHawk]

Good info on the alarm. It looks so simple, I wonder why I couldn't find a circuit schematic to make one up myself.

I need some help too, now, to figure out why my tacho stopped working. It's raining today, so I can't get it into the garage to get under the dash.

thx

[Daniel]

Think about this. Dark night and you loose a headlight for whatever reason that it blows a fuse. Oh, yeah, Your driving in the mountains at 60 mph. I want TWO fuses. I also want my high/low left/right on different fuses and relays.If a stone pops my left light and it blows the fuse,I still have my right because its on a seperate relay and fuse. This is the correct method. Please don't risk your life on those that guess at a resolution.

[TomoHawk]

Then why did the engineers run BOTH lights through just the one switch in the original wiring? You have a fuse for each light, but they both go through the one switch.

[Zedrally]

This is common in DC circuits.

I'll try to explain the best I can Tomohawk:

In DC systems the load is always place before the switch and by convention the fuse. Placement of the fuse, either before the switch or after is another argument, often debated with no right answer...

Reasoning for this is that the load [headlight, in this case] consumes all the power and any current flow after the load is reduced. this then requires a smaller switch and fuse than would normally be required.

Think of it this way, a headlight is rated at 55watt IIRC, that 55 watt or most of it would be consummed in heating up the filiment to produce illumination of whatever brightness. If for example it uses 50watt, then 5 maybe left in the circuit flowing towards the switch, fuse.

This my understanding of why the wiring diagrams appear to be "wrong"...

Anyone else like to enlighten us...

MOM

[Daniel]

Tomo, He is still using one SWITCH for on /off. My point is that a RELAY is held in the on position by electricity. Should something occur that shuts off that power to the relay it will drop out. That is the concern. Remember you are discussing ADDING relays. Sure the factory used a single switch,it being turned on/off manually it doesnt care about the status of the electrics. As for fuse placement you would want it as close to the power source as possible. The fuses job is to protect the wiring.If you have a 10' wire and fuse is on the end away from the supply.Should that wire short behind the fuse it will melt and burn because it has no protection. With the fuse at the power source the total wire length is protected. Think about your house. The fuses(breakers)are as close as possible to where the power is supplied.Even if you have a sub-panel(secondary panel) at another location in your home it is FIRST fused at the nearest point to the supply. I hope this helps develop a thought or two.