Daytime running lights (DRL) are a good idea, they make the vehicle easier to see, especially if your blind and failed to see this oversize house coming at you down the road.
Sarcasm aside, I drive with the DRLs on, but I don’t want them on when I’m parked and the engine is idling, i.e. truck stop, road side rest, campground, driveway, etc.
Unfortunately, there is no way to turn them off, UNTIL NOW.
On the Ford F53 chassis, the DRLs are not a separate light, they use the regular headlights as the DRLs. When the headlights are not turned on, voltage for the lights is sent thru a resistor to reduce it making the headlights shine a little dimmer. Power to the headlights/DRL circuit is on anytime the ignition is on.
After studying the Ford circuit diagrams, I elected to tap into the headlight circuit so I could enable / disable power to the headlight circuit.
If my HEADLIGHT switch is OFF, the trucks headlights or DRLs will be off.
If my HEADLIGHT switch is ON, then the trucks headlights / DRL will operate normally depending on the trucks regular headlight switch.
The HEADLIGHT switch operates a standard 12 volt cube relay. I decided to not hook up the light that’s inside the switch as I find these distracting, especially at night. If you want to hook it up, you might tie it into the instrument panel lights so it can be dimmed.
Normal headlight power comes from a relay located in the engine compartment, it then comes into the vehicle and goes to the Central Junction Box (CJB) . This fuse panel is mounted on the inside of the firewall If you remove the headlight switch panel on the left side, and look in there, you should be staring right at this fuse panel. You can also reach it from underneath, but you’ll need to get at it from the front, as you’ll see in a moment.
The power wire we are looking for is black and has a pink stripe (BK/PK). Its located in the wire bundle that goes into the top of the CJB.
I used a small sharp pocket knife to cut the wrapping off of the wire bundle, then carefully separated the wires until I found the correct wire. After double/triple checking the color (black / pink) I started the truck, had my wife watch the DRLs, then cut the wire. The lights went out, (phew, got the correct wire)
I then spliced the cut wire into the relays normally open contacts (#30 and # 87)
We tested to ensure the my HEADLIGHT switch worked correctly, when it was OFF, the DRLs and headlight did not come on. When the my HEADLIGHT switch was ON, the relay energized and the DRLs and headlights worked normally.
I mounted the relay to the inside of the firewall with a short screw, then re-wrapped the wire bundle and tied the wires up with wire ties.
You can see this entire article on my web site.