Like all of the electrical wiring in Audis, the headlight wiring is a bit weak. Below are some instructions and tips for adding relays to power the bulbs directly from the battery or alternator, and just using the stock wires to trip the relays. This will give you more power at the bulbs and less strain on the original low gauge wires and headlight switch.
- Always use silicone dielectric grease on your electrical connections for longevity, and use rubber boots on the new headlight plugs.
- I recommend using one relay for each pair of filaments. If I remember correctly a 55W bulb will draw 4.3 amps and a 100W will draw 7.6 amps, or thereabouts. If you end up using 55/100W H4's and 100W H1's, and only use one relay for the high beams, then you will draw 30.4 amps. Most relays are rated for only 25-30 amps, though I've heard of some 70 amp Bosch relays (but I'm sure they're a lot more expensive than two 30 amp relays).
- Pop the wires from the headlight sockets (use a jeweler's screwdriver to reach into the socket and press down on the locking tab) and cut off the terminal. This will give you the most usable wire. Run this wire to the trip circuit of the relay.
- Use 10-12 gauge wire from the battery to the relay and from the relay to the headlight. Be aware that the tabs on the Euro headlight bulbs are not standard .250" width. They are .312" wide. You can get the proper terminals from AMP. You should probably beef up your ground wires too.
- Very important: Install in-line fuses to each of the wires going to the battery as close to the battery as possible.
- Use relays that have 2 output terminals (one for each side -- much easier than trying to crimp two 10 gauge wires on one terminal.
- The relays should be installed as close to the headlight bulb as possible for maximum candle power.
- DigiKey (800-DIGIKEY), Newark Electronics (800-463-9275), and many other electronics distributors sell PotterBrumfield (now Siemens) automotive relays in a case configuration which is weatherproof and has a mounting bracket. Cost is about $7/ea. Connectors on the bottom are push-on. There are also plastic relay mounts that clip to the top of some of the vw/audi fuse panels. The relays are P/N VF4M-65F11. Be sure to order the mating connector shell, a VCF connector for each relay, and enough terminals (get a few extra to practice with). The connector shell is P/N VCF4-1001, the VCF connector is P/N VCF4-1002, and the terminals are P/N 26A1349A. They've also got waterproof in-line fuse holders for 0.25" x 1.25" fuses (Bussmann P/N HFB-10) and 30A fast acting glass fuses (Bussmann P/N BK/AGC-30).
- Consult the diagram below for an example of wiring relays to H4 bulbs.
