Headlight Relays

I recently converted from a generator to an alternator which greatly improved the brightness of my headlights. I heard that adding relays would help even more and would be an inexpensive and fairly easy project. The factory setup has 12-volt current traveling all the way from the battery to the headlight switch in the dash (which is part of the fuse box) and then heading back through the foot control switch (which you press to switch from bright to dim) and on to the headlight bulbs. That's a long way to travel, especially through often inadequate wires manufactured in 1962. There is a lot of resistance in the switch and along the route. The voltage needed to make your headlights be as bright as possible can drop quite a bit.

There are several links at the bottom of this page that explain the theory behind relays in great detail. I took a few photos of my project and made a few notes. I was measuring 12.8 volts at the battery and 11.2 volts (640 lumens) at the headlight before I put in the relays. After installing them, I was getting 12.5 volts (920 lumens) at the headlight. Not a bad payback for a project that cost less than $20 and a few hours of the weekend to do.

One thing I wanted to avoid was just screwing two black plastic relays to the side of the engine bay and soldering the wires to it. I decided to gut the old regulator from my generator and install everything inside. This would look less obvious and appear as though it could have been factory. I had to cut the tabs off the relays and mount it to the relay base with double-sided tape (the kind with spongy material inbetween). I used holes that were already in the base to run the ground and power wires and drilled a larger one for the other four wires. I put rubber grommets in the holes so the sharp edges wouldn't cut the wires. I soldered all connections and used 10-gauge wire to the battery and 14-gauge for the other wires. The ground wire runs under the unit and uses the same screw that attaches the unit to the engine bay wall.

This shows a close-up with the different wires and where they attach. The relay instructions should also show where the wires go. The fuse holder was held on with zip ties and can be changed without having to remove the cover.

The first step (after disconnecting the power at the battery) was to remove some of the harness wrap to expose enough wires to splice. The two wires you cut are the ones from the foot control switch that go to the headlights. In the case of my `62 Falcon, they are the red wire with a black stripe and the green wire with the black stripe. Check the wiring diagram in your manual for specific color codes.

This shows the completed connections before being wrapped in electrical tape. I soldered each connection and covered them with heat shrink tube.

I wrapped the wires in electrical tape except for the new 10-gauge wire that runs to the battery side of the solenoid. Since I was going to use standard bulbs and not high output xenon lights, I kept the factory wiring to the headlights.

I moved the horn relay up and installed the new relay box under it. This is on the driver's side radiator support.

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