Headlight Relay Diagram

[Calimus]

Been meaning to post this for a long time but couldn't find the file. Re-discovered it tonight. Granted this is for a scirocco, but it's easily applied to a cabby.




Here's the link to it if you want to view it seperatly and download it that way.

http://www.toplessrabbit.com/forumpics/relaydiagram.jpg

[PDX Cabby]

that is one of my favorites of all the wiring diagrams for wiring headlights.

Since i have a light fetish, i have 2 relays for each light (just as this one shows). Most of my friends and other relay diagram only show 2 relays total, splitting the load between each light.

All you need to convert this to a cabby is to disregard the "driving light." If you have a single round grill, you'll also need to disregard the "High Beam" and plug directly to the 60+W input on the "Low Beam"

An alternative to the "20 Amp Fuse Quad Tray" is to get fused relays. This puts a spade fuse on the top of the relay. A little less wire splicing as well.

To make things easier (i've seen this quesiton come up a lot) the Green lines running switched power) are already in the car... they're the ones that are currently running the headlights...

[Calimus]

Yep, what he said. Was going to add all that myself, but I didn't have time when I posted the pic. But, you hit the nail on the head with your comments

[Blades]

I'm doing this soon, I'll post pictures.

That's from my friend ATS website

http://www.longcoeur.com/scirocco

He's an old buddy of us. The Scirocco master.
Quebecois au Texas

This tech notes
http://www.longcoeur.com/scirocco/tobedone.html

3 Important points
http://www.longcoeur.com/scirocco/Techn ... index.html
http://www.longcoeur.com/scirocco/Techn ... index.html
http://www.longcoeur.com/scirocco/Techn ... index.html

read them all

[Calimus]

Yup, thats Pats Diagram. Got to meet him 2 years ago at the Scirocco.org get together. He's a pretty damn funny guy.

[PDX Cabby]

ohyeah
relay part # 141 951 253B

[BigDaddy90Cabby]

here we go, this just may help me to understand about all of what you all are talking about.. i hate being new at something

[gull]

I'm about to do this myself. I just thought I'd add a couple suggestions of my own:

- Consider using circuit breakers instead of fuses. You can get self-resetting automotive circuit breakers for only $3.75 each here: http://www.wiringproducts.com/contents/en-us/d60.html. Four of them would cost you less than $16, about the same as a fuse box plus fuses. These little guys might save you fumbling around in the dark with fuses, some day, plus they'll recover on their own from an intermittent short. (I think circuit breakers are also a good idea for other "mission critical" stuff, like radiator fan circuits, where you might want to recover from a momentary overload. You can get ones that will plug into the stock fuse panel like a fuse.)

- The two-relay variations I've seen often put one fuse on the hot side of each relay. I don't like this because it means one blown fuse will cost you both low beams or both high beams. A better solution is to put the relays in the ground side of the circuit. You still use two fuses, but now one fuse handles the left headlight and the other fuse handles the right headlight, with power going to the common terminal for the two filaments in each bulb. Now if a fuse blows you still have one headlight on in both beam settings.

(Edited for clarity.)

[Calimus]

I think the reason the fusebox is added to that diagram is just because it's simple & compact. That, and I doubt too many folks think as far as using resetable breakers on such low voltage. However, that doesn't mean you don't have a great idea.

In my case, what I did with my rocco is go to a setup that uses an inline fuse (blade style, same as the car). Generally, you should never overload these setups unless you are tinkering with the setup or used some craptastic wire that can't handle the load. Even then, sometimes there are those issues where you do everything right but something still happens.

it's defintily another option and a slick one at that

[gull]

Yeah, I was going to go with fuses, but I looked at the price of a fuse box with a gasketed cover for under hood use, and then I looked at how much the thermal breakers with mounting tabs cost, and thought, "why not?"

Agreed that you should never blow one of these fuses if the wiring is done right. Assuming you don't hit a deer or something.

I have an inline fuse for my ham radio gear. For this, though, I need at least two more fuses and I don't really want a bunch of inline fuse holders flopping around under there; I want to do a neat and tidy install for once.

[gull]

Well, it's done. I got very similar results to what others have reported -- on high beam I went from 11.0V across the headlights to 13.3V, which ought to give me more than half again the light output I had before.

I mounted the two relays and two circuit breakers on the passenger side inner fender, just ahead of the strut tower, because there was room there. Power came directly from the alternator output stud since it was handy, and for ground I tapped into a nearby 10 ga. wire direct to the battery post that I'd put in for a radio install. I chose to reuse the existing headlamp sockets and just splice close to the socket -- since I'm not running upgraded bulbs, current-carrying capacity isn't a concern, and the remaining inch or two of 16 gauge wire doesn't add enough voltage drop to worry about. I also kept the existing short harnesses from the main headlamp sockets to the auxiliary high beams -- again, just not worth replacing. The inner high beams draw about 5 amps each, and one foot of 16 ga. wire only drops 0.02V at that current level.

Safety First meant that everything had to be top-notch, so I soldered all splices and then insulated them with heat shrink. All ring lugs and such were crimped, then soldered and insulated. The relay socket contacts and ring lugs got a coat of dielectric grease before they went together, to stave off corrosion.

As a side benefit, I no longer hear the fuel pump slow down when I switch on the headlights. As far as I know this never caused any problems, but I always hated hearing it running on lower voltage, because it seemed like it couldn't possibly be good for it.

[Calimus]

Sounds like a nice setup. Any pics?

[gull]

Don't have any right now, but I could take some if there's interest. The wiring diagram would probably be more useful than photos, though, maybe I should scan that in.

[gull]

OK, here you go. Those of you who do those super neat and tidy stereo installs that I've been looking at in other threads are gonna laugh at my crude workmanship, though.





The red things that look like Lego bricks are rubber covers over Bussman ShortStop circuit breakers. (And yes, a couple of those relay wires are a bit tight. After seeing the photos I went in and re-dressed them with more slack. Funny how these things don't show up until you look from just the right angle.)

And here's the wiring diagram -- click for a larger, hopefully legible version. I apologize for the hand-drawn diagram but it was originally just for my own reference.

Wire colors marked with a * on the diagram are the color codes in the existing harness.

A few notes:
- It would have been far more efficient from a wiring standpoint to mount one relay on each side of the car, putting the relays near their respective lights. The only reason I didn't do it that way is there isn't a lot of room to mount anything on the driver's side of the engine bay. I was having a hard time finding a spot to mount a relay over there that wouldn't get in the way when I needed to change the air filter, fuel filter, or battery, and goodness knows there's enough in the way already. It ended up being easier to just mount both relays together and add a couple more wires to the bundle I already had crossing the front of the car.

- I'm running stock bulbs. For higher wattage lamps you'd want to uprate the circuit breakers, relays, and wire sizes accordingly.

- The 10 ga. red and black wires near the top of the photo are for an unrelated 2-way radio install, although I did tap into the black one for ground, since it was already headed over to the battery post.

[Calimus]

Not bad at all. Much thx for the wiring diagram, will come in handy should I ever need to build another one for the cabby. I'll have to take some pics of the cabby's current harness as it's far more revamped then the diagram I posted for the rocco. For that matter, my rocco harness has been drasticly revamped over the years.

An nothing wrong with your wiring job. If it works and your happy with it, thats all that matters.