Accessory fog/spot light wiring question

Hello, I'm adding a pair of fog lights and a pair of spot lights to a light bar on my 2016 Tacoma.

I want to do this without adding extra switches inside. My truck has the factory fog lights and I want to switch the relay for the accessory fog lights by tapping the power wire to the OEM fog lights.

I want to do the same with the accessory spot lights using the high beam of the headlights.

I'm pretty sure I can figure out which wire to use from the wiring diagram so my main question is will this cause any problems with the body control module? I'm not sure if it will trigger any sort of bulb wiring failure warning lights on the dash.

Thoughts? If anyone happens to know the hot wire to the high beams and the OEM fog lights that would save me some looking.

Thanks.
Todd

 

I don't know, but I suspect it might; one of the issues is the resistance sensing circuitry that lets you know when a light has failed; tapping into the light circuits in the way you've described could cause the system to think there are problems. I would consider taking power for your new relays from the control side of the existing relays. I don't think that should cause any issues.

 

Interesting idea, I'll test that. Thanks.

 

Confirm the power draw of the new lights does not exceed the capacity of the existing wiring and fuse.

 

I think his intent is to run new power lines, but to control them via relay, using existing circuits.

 

This is correct all new fused power and relays. Just triggering the new relays with the signal from the OEM wiring.

Hella Fogs in the center and spots outside. Temp setup to confirm the clear the grille.

 

I highly recommend that you add switches instead. If you use the high beam fuse as the source for the relay power, then add a switch in the cab you can have the options of using them with high beams or not.

For fog light I would again add a switch using switched power as the source. You could run the lights anytime the truck is on.

Factory fog light power will shut off when you go to high beams- and splicing onto factory harnesses can get sketchy.

 

You may add switches on wires from relay to C11 intercept harness.
Fog tap will not turn off when High Beams are selected, and ON with ignition and Fog switch ON (unlike the OEM circuit).

 

You could use a 5 pin relay, then determine if its easier to use the existing fog or highbeam circuit to trigger the switch-over from your fog circuit to auxiliary-High circuit legs.

 

None are "available" at the engine bay fuse/relay box.
C11 is under the steering covers in the cab.
And yes, the circuit are ground actuated.

 

Never mix street lights with off road auxiliaries.

This is a terrible idea.

 

Simple on/off/on resolves any "legal/inspection" issues...

 

I would argue that putting a switch on the 86 pin is not only easier to install, but it is easier to troubleshoot, it's just as clean, and there's no chance of accidently triggering the wrong light in traffic.

I won't go into the "considerate/inconsiderate/legal" debate, there are definitely multiple die hard viewpoints on that issue.

 

I appreciate the input. Fogs are working now. Spots are close.

 

So, is this a practical application? Not trying to be a dick.

 

I was talking to a friend the other day about switching the positive feed to the relay vs the ground side. What is the logic of switching the ground side?

Is the reduction in wiring the only reason? By that I mean that you can take power from the primary hot feed to the relay to power the + switched side.

Regardless, The lights are on the truck. both sets of lights are independently powered, fused, relayed(?) and only take a signal from the OEM harness. I took a trigger + signal from the OEM fog light wiring. The spotlights are triggered by a + signal from the drivers side high beam socket wiring. The signal wires are inside a harness cover that is taped on and secured to minimize the risk of a short due to vibration/chafing.

I'm aware of the potential driver to driver issues having things wired this way and accept that responsibility. I'm not trying to build a bad ass adventure truck. I'm going to have to be driving in an area that has long unlit roads with many potential animals crossing from the woods. The area also has seasonal ground fog and snow storms. I don't want to have to move my hands to find a new switch and I don't want to pull wire through the firewall and panels. These new lights are operationally in parallel with the OEM lighting.

I think I'll be much more cautious about having high beams on and I'll certainly be able to notice they are on. Fog lights are amber and lower wattage and as such are road legal to run anytime.

A note, If you are offering advice to people who are asking a genuine question please think about separating your personal opinions from the technical aspects. If you disagree with my wiring them to run with the OEM equipment because you think it creates a rudeness situation that's fine. If you think it creates an electrical issue, which was my question, that is helpful. I'm new to the forum and came to have a technical question answered. I welcome your personal opinions but if you really want to help someone...

Just a thought.

Glad the community is here for everyone.

 

Just think you went through all that trouble and then left the controls up to the factory wiring.
So your extra fog lights only work when the stock fog lights are on with low beams,
and your spots come on every time the high-beams are on no matter what.

I've got two sets of driving lights added using switches and the highbeam trigger. The pocket lights are Sport models, less powerful, and combo lenses to fill in with the highbeams in usual highway driving. The ditch lights are Pro models with spot lenses for seeing wildlife on the roads, they have an additional foot switch so I can kill them if I meet any traffic. Most of the time they are covered and turned off.

Running wires through the firewall is nothing, and panels and switches are available to make the interior look cleaner than oem.

Enjoy your lights though, they look great. I used to run aircraft lights on my old 86 - tons of light and heat! Melted my share of relays, lightcovers, and fuses with those big halogens..

 

Back in the day when I had driving lights on my MG we often joked about adding landing lights. I always wanted to try it. If they are a problem I'll switch them out. Regardless I won't slip into old age wondering about doing it.

I really do appreciate the knowledge base on many vehicle specific forums. I ride an old Yamaha SR500, I have an early GSXR1100, A Ducati Paso, A series IIa Land Rover. All the forums related to those have been helpful and I enjoy being able to contribute to the knowledge base.

 

Just run your numbers and make sure your components are beefed up - those 500ff are 50w ea so that circuit needs to handle ~10 amps, My old 100w aircraft lamps needed double that around 20amps - when I put four of them on one circuit it fused a regular 40amp relay open permanently.. lol at my 16yo self engineering on the side of the highway..