Here is the wiring diagram for my plow light switching. It shows optional inner 5-1/4" driving lights. The four relays are "double switched": two of their trigger coils are fed 12 volts by the low or high beam signal, and either one of those are grounded by the plow light switch. At any time, only one is on - a high or low relay running either regular lights or plow lights. A 20A fuse or circuit breaker protects the incoming main power wire, which is directly connected to the battery or alternator.  The two relays on the left can be turned on if the plow light switch is on. The two on the right can be on if it is off. The high beam switch energizes one each of them and likewise the low beam setting energizes the other two. This table explains this a third way, just to make it clear (relays are numbered left to right). The relay number in each box is "on" when the switch positions above it and to its left are chosen:
Each relay runs two bulbs, except the "normal-high" one (3), which might also be powering the auxiliary driving lights. If I do use them I will add a second relay in that postition, wired exactly the same, for the driving lights. A single 20 A fuse or breaker will suffice for the entire circuit, unless, again, I install those driving lights, in which case that fifth relay will get its own 20 A protection. I know this looks complicated, but it isn't really. There will be a relay/breaker block mounted on the passenger side inner fender near the battery, with four small wires coming to it from the switches on the dashboard. One heavy wire from the battery powers it, and fat wires will run to the various light sockets.The relays and holder will be ex-Audi, since I have tons of old Audi parts accumulated. I'll get some new headlight socket pigtails, and try to find some nice lighted switches in several configurations to do all my new circuits. |
