Here are a series of questions I had. This is in the lighting thread. Answer #4 may help you.
Suggestion, don't wire your driving lights in with your fogs. This will defeat the function of the fogs, and likely be illegal. In most states you can only have 4 bulbs illuminated at one time, on the road. I wired my driving lights to go on with my high beams which is both legal and useful. I also added an additional diode across the relay coil to prevent back emf. I posted later with my results.
Originally Posted by SilverSport
What if you posted links to the other info threads like Hilldweller's, etc?
Stan - I will take a shot at your questions.
1) Yes. It takes 12 volts but very low amperage to energize the relay.
2) Yes. Put the switch on the signal lead from the highbeam circuit to your relay.
3) Fuse the power wire from the battery that the relay on the secondary circuit will control.
4) Pulse width modulation will destroy the relay very quickly. Here's a link to a schematic for adding a capacitor to ensure constant 12V to the relay:
5) 100w divided by 12V = 8.3 amps X 2 = 16.6amps so 20 amp should be sufficient.
6) Run dual wires from pin 87 on relay, one for each light. Run a ground wire from each light to a common ground.
7) 14 gauge is fine for signal circuit. 10 or 12 gauge for power from battery to relay to lights.