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Adding relays for your headlights

Igor Kessel's wiring instructions:

Pictures: (click to enlarge)
Very large GIF diagram

Some people get power for the relays from the back of the alternator. I used the jump-start post instead. I found it much more accessible. Use a heavy gauge wire with a hermetically sealed in-line fuse. My lights are 560w total= 560w/14v=40a max current. It's a good idea to exceed this value by ~1,5 times for both the fuse and the gauge of this main supply wire; use either 6 or even 4 AWG. I also suggest that you choose a RED color (international convention for a *hot* wire) or a YELLOW (Alpine tradition for a const +12v, whereas RED is for switchable/ignition +12v). I personally always follow the Alpine convention (after having installed the first hundred of their HiFi systems it kind of gets in your blood forever:) Of course after you feed this wire to the main bus of your custom made fuse/relay box you may choose the smaller gauge/fuse for distributing the power to 4 individual relays.

Let's say you have my set up with the most current consuming beam being a HIGH with 100w H4 + 100w H3, 200w total. 200w/14v=14a, so you'll need to use no less than a 14 AWG wire with a 20a fuse. I strongly recommend that you use 4 individual relays and 5 fuses for the Euro-light wiring. I saw a lot of horrible wiring on Quattro clubs, mostly the el-quicko jobs where a single relay, mounted upside down (I guess to simplify the access to the terminals) carries out all the current switching. Needless to say that the terminals of said relay are always corroded to the point when they are green, thus creating overheat and the subsequent failure of the circuit.

If you find it difficult to build a NEMA-4 watertight relay box, you should at least mount the relays with the terminals down. In this case DO NOT use electrical tape for isolation. Use the heat-shrink female spade crimp terminals instead. Yes, they are expensive (like 2/$1), but are well worth the price. You can get enclosures from a number of catalogs: Newarc, Mouser, DigiKey, McMaster-Carr etc. I forgot where I got mine 2 years ago. It is a polycarbonate clamshell with a rubber gasket in the groove on the perimeter and has internal bosses for mounting a PC board. The size is approx 15x10x8cm, small enough to be mounted in the cavity under the resistor for the radiator cooling fan. All 5 fuses are in-line, in cylindrical waterproof cases, made out of yellow Si rubber.

Do it right, take your time, use heat shrink tubing, wire ties, split looms and try to do the job as neat as possible. The reward would be a bullet-proof installation. I have yet to see an electrical failure on any item of the tons of aux equipment that I always install on my cars. Ever. The key is to avoid what we call *spaghetti wiring* at all cost.

Look at this image for Igor Kessel's relayed wiring harness schematic.

http://members.aol.com/c1j1miller/eurowire.html

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Other Details:

You can purchase the Audi connections for the lights mentioned above in Peter's post, or buy your own female wire connectors, and go to Home Depot for a rubber boots for the wiring connection. Home Depot internal reference 5200-BCZ, bar code 81786 20040, made by Bryant.

Denon has been including some cheap H3 and H4 bulbs with the lights. The city lights take a small base bayonet style light (single bottom terminal, with two protruding mounting studs). I went to Pep Boys and bought some "european lamps" for license, parking, and side marker lights, Sylvania 3893 BP. There's no marking as to wattage; I'd guess no more than 4-5 watts. I think if you use too high a wattage bulb, you'll throw a lot of scatter right up front which might be bad in fog, etc.

Make sure you install all the necessary bulbs before installation; once the lights are in, you _can_ change the bulbs; however, you'd better have pretty small arms, and not have a hot radiator.

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Page last updated: April 28, 2003