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92-95 Civic, Headlights switched with ignition, DIY
I've gotten sick and tired of leaving my headlights on when I leave my car. So I wired them to switch off when the key is out of the ignition switch.
I first went to the combination switch, and installed a relay into the supply power. That turned off the headlights, but left the running lights on, there has to be a junction before the combination switch. So I went straight to the source of the lighting circuit, the fuse box under the hood. There is a 40 amp PAL style fuse that protects the headlight and running lights in the car. With no easy way of installing a relay in place of the fuse, I had to take apart the fuse box to get to the wires.
I first made sure that what I wanted to happen, will happen. The circuit I'm looking at is protected by the 40 amp PAL fuse. I want to keep the fuse, so I have to connect a relay past the fuse to control the headlights with a switched ignition power supply.
With no key in the ignition, I switched on my headlights, and turned on the headlights. No surprise, the headlights work. I then turned off the lights.
I pulled the 40 amp fuse and turned on the headlights again. This time I had no running lights at all. Just what I want to happen if I leave the combination switch on with the ignition off.
I had to pull the battery out of the car to make space to pull the fuse box out. Also disconnected the fuse box power supply cable and the alternator cable to be able to remove the fuse box from the car. Disconnect the negative from the battery first.
There are three 10 mm bolts holding the fuse box down, and a plastic cover on the bottom of the fuse box that need to be removed. Then the connectors unplugged, and then you can remove the fuse box from the car.
The common power supply is on the left side of fuses.
With no fuse installed, there is no continuity between the left side and right side fuse lugs.
With one lead on the output side of the 40 amp fuse, I could then run a continuity check to determine where power goes on the bottom side of the box. There is only one output into the wire harnesses. The middle wire of this three port connector.
I want to install a relay at this outlet, so I need to pull the middle wire out of the plug. I don't like cutting my harness up, and chose to proceed this way, you can cut the wire to install your relay, if you want.
Have to take out the wire lock, and then use a pick to release the terminal lock inside the connector.
So I happened to have a spare piece of wire with a terminal that fit this connector. I installed this into the three port connector, and extended the wire to reach my relay. The original wire (that went there) is extended (from the loom) with a spade connector and a piece of wire that reaches the relay.
Everything is taped off, and gently made to fit inside the bottom of the fuse box before I install the lower shield. I did cover the wires to the relay with conduit to help protect them (not shown).
The relay behind the battery, and next to the fuse box. Relay is grounded on the 10 mm bolt that holds the fuse box in place. I already had an ignition-on signal wire controlling another relay (for fog lights), so I tapped into that wire to switch this relay on and off.
My switched ignition source. The yellow wire with fuse to protect the wire. This runs to the two relays I have for lighting (headlights/running lights and one for the fog lights).
After everything was back in, this worked just like I wanted. With the key in, I can control the headlights with the combination switch, and if I forget to turn off the headlights taking the key out of the ignition turns them off.
I'm really stoked to not have to deal with a dead battery again because Honda couldn't just make this a feature to begin with.
92-95 Civic, Headlights switched with ignition, DIY
