Fog lights, fuses and wire gauge

I am planning to put fog lights on my 2020 SR. Seen one video where you do a tap splitter and push through the firewall to wire it. But, saw another where the guy only wired the fog lights into the existing headlights, his being a 2017 SR. Per him fog lights go out with hi beams. Seems pretty simple, but... What's the current draw for the head light fuses and should or could I increase the size of the fuse without an issue. The guys who do the tap use a 20a for the fog lights.

 

I would very much not recommend simply tapping (hacking) into the factory headlight harness to add a set of fog lights. All you're going to do (if you do that) is assure wiring problems down the road a few years. Do yourself a favor and install the fogs with a proper switch, relay and wiring all installed by somebody competent. Trust me, it's not all that difficult and there are plenty of threads here showing how to do it if you search.

 

Typically the relay power is tied to the Headlight Low Circuit.
This will only allow power to the relay (with the switch ON) when the headlights are on Low.
Traditional use of Fog Light are for “Fog” where you don’t want high light output aimed Upwards.

If you want to have the ability to use the Fog Lights at any time, ONLY WITH THE KEY IN THE IGNITION AND TURNED TO ON, pull power for the relay from a circuit energized with the key ON.

Or if you want the ability to use the Fog Lights anytime, tap the relay to a circuit that is energized all the time. (I would NOT use a circuit such as EFI, ignition, ect)

Again, This is only power for the RELAY not the Fog Lights themself.

I would NOT supply power from any place other than a dedicated relay for the Fog Light.

 

Thanks, it did seem too easy. Not a problem, I have the kit with all the trimmings and an OEM fog light switch coming.

 

One other question, the kit shows possible ground and power connections to include the battery. Just to be sure, if I connect via tap at the fuse box, I shouldn't also make a connection to the battery and I need to only ground it in one location, not 2.

 

No, you’ll still need to tap battery power for the fog lights them self.
The Relay and Fog Lights both need a ground.

Ground the relay close to where you mount it.
On most after market light kits the switch powers the relay.
So you tap power from a fused location in the truck.
Then to the switch, and out of the switch to the relay.


————————————————————————
*The OEM TOYOTA Switch supplies a GROUND to the Relay*
I’d strongly advice using an aftermarket switch if you want the switch to work properly.
Or maybe @Muddinfun knows a work around?
————————————————————————


Ground the Fog Lights close to where they are mounted.
Sometimes they have a separate ground for both lights.
Sometimes they are tied together and share the same ground.


To get an understanding of how a relay works, you can read this nice write up.
https://www.12voltplanet.co.uk/relay-guide.html

-Fog Light Circuit-
Battery -> Relay
Relay -> Fog Lights
Fog Lights -> Ground

-Relay Energized Circuit-
Fused power -> Switch
Switched Power -> Relay
Relay -> Ground


Let us know how it turns out for you!

 

In another thread, I proposed a way to cut traces and install jumpers inside the switch, but that was just a theoretical hack and definitely not for people with limited wiring experience.

 

Sound like an aftermarket switch would be “easier”
And I’m all for easier.

 

Thanks for that timely heads up. I would have certainly failed the first test. Waiting for the other switch, will evaluate when it comes then start the install. Article on the relays was very interesting. My hobby car is a '71 MGB where Lucas Electric is known as the 'Dark Prince'.