Question about using pre-made wire harness

[Frank69]

I'm putting a pair of Speedway Motors fog lights on my 68 SRL-311. I have a pre-made wire harness for auxiliary lights leftover from a Jeep project. I used two of them on that project and they work great. A wiring diagram of one is below.

diagram of lights.jpg

I've also included closeup of the lighted rocker switch that comes wired in this harness.

IMG_2718.jpeg

and my current fog light wire terminals (the two smaller diameter bullet plugs. The larger is hot when the headlights are on. Not sure why this is there)

IMG_2717.jpeg

My question is can I cut this switch off and wire this into the OE/stock fog light circuit, thus utilizing the factory light switch? I'm pretty sure the switch wires are White-hot/common, Black-ground, and Blue-"on" led light in switch. I've already tested my existing fog light wiring by connecting directly to the new fog lights and it is working. My concern is that the existing hot lead is carrying approximately 12v from the dash switch, so not sure this will be compatible with the new harness as currently laid out. I can always cut this harness up and just use the parts I need, but they did work pretty good in the Jeep. What do you think?

[Habitat.pat]

Frank, off hand it looks like what you propose will be fine. The only current going through the dash fog switch Willie be to power the relay, the power for the lights comes through the fuse directly from the battery. This assumes that you are actually connecting fog lights & not driving lights.

If they are driving lights, I would have one suggestion. Supply the power to the fog light switch from the high beam headlight circuit so the driving lights will be on at the same times as the high beams. That way you don’t have to remember an extra operation.

Peace, Pat

[Frank69]

Quick update. Did a test/temp connection using the harness. The blue and white switch wires have to be hooked up to activate the fog lights. The black wire needs to be hooked up for the switch indicator light to function. Disconnect the black wire and the fog lights are still on. Connecting the three new switch wires in turn to the red lead from the OEM did nothing, except get really HOT when I tried the blue one.

[Frank69]

Frank, off hand it looks like what you propose will be fine. The only current going through the dash fog switch Willie be to power the relay, the power for the lights comes through the fuse directly from the battery. This assumes that you are actually connecting fog lights & not driving lights.

If they are driving lights, I would have one suggestion. Supply the power to the fog light switch from the high beam headlight circuit so the driving lights will be on at the same times as the high beams. That way you don’t have to remember an extra operation.

Peace, Pat

Thanks, Pat. They are fog lights, so I’d like to utilize the pull and turn function on the original switch.

[Frank69]

Ok, grabbing the main harness power from the original hot lead for the fog lights does work. When the original switch is turned, power goes to the relay and activates the new fogs. Isn’t this defeating the purpose of the relay though? I wanted to grab harness power directly from the battery and just use the original dash switch as a trigger.

[Frank69]

Ok, I pulled the harness apart and found that the white wire was coming to the switch from relay post 30 (main power). The blue wire goes to 85, so there’s my trigger. This harness uses 86 for ground, no problem. 87 goes to the fog lamps. I eliminated the white wire altogether and hooked it up. Blue-85 to existing 12v from OEM switch, 30 to new lead to battery, 87 to fogs, and 86 to battery ground. Voila! New fogs. Let me know if I could do it a better way.

[redroadster]

Tradition fog lamps are high amp
Usually the . Neg is the trigger to the relay coil swt. Pos cuts at ign swt. ,pos sucks power / current to it , not from it

[Frank69]

Tradition fog lamps are high amp
Usually the . Neg is the trigger to the relay coil swt. Pos cuts at ign swt. ,pos sucks power / current to it , not from it

Thanks. I tried with just the blue wire coming from relay post 85 and it worked. Just to be safe, I added a wire from 86 to the OEM switch ground wire. No difference, but more peace of mind. In retrospect, I should have just made the harness myself as these pre-made aux ones use very thin wire and are designed for LED’s.

[Curtis]

That harness is bit overly complicated. All you need for fogs is fused power to the relay, power out to the lamps and ground. Use one of the fog light terminals from the harness to trigger the relay and ground the other terminal. This takes the power out of the switch and it functions as original.

[Curtis]

Just finished this drawing.

https://kendo-usa.org/datsun/datsun_fog_layout_68.pdf

[Frank69]

That harness is bit overly complicated. All you need for fogs is fused power to the relay, power out to the lamps and ground. Use one of the fog light terminals from the harness to trigger the relay and ground the other terminal. This takes the power out of the switch and it functions as original.

Thanks, Curtis. That’s essentially what I ended up with after eliminating the non-essential wires from the pre-made harness. I just had it laying around after putting auxiliary lighting in my grandson’s Jeep. I may end up redoing it with larger gauge wire.