I think you mean, at night when the running lights are on, you want to be able to toggle them off/on with an upfitter.

Or do you mean, during the day when the running lights are off, you want to be able to toggle them on/off?

Pick one, because making it work both during the day and during the night will get complicated.

I believe the easiest way will be to interupt the lead running to the bumper plug for running lights with a relay. Use the NO or NC contacts depending on which way you want it to operate, as I described above. Then just power the relay with an upfitter switch output.

The trailer lights are already isolated from the truck lights, so should be no problem with backfeeding.

 

I do mean when my running lights are on, I run with my lights on every time I tow, day or night.

I was hoping not to run a wire from the trailer plug back to the cab and the switches. I thought it could be done from the body module under the hood. I'm not sure what you mean by NO and NC, [terminals on the relay?], and doesn't each upfitter switch have a relay already? It is going to operate just the trailer lights so it won't be drawing that much amperage.

 

NO = normally open
NC = normally closed

Most relays have one set of each, NO and NC.

I don't have your later model truck, so I don't know where the various fuse blocks are located. But I would guess you can do this under the hood. All you need to do is trace the wiring, or check your manual for where the trailer fuse/relay box is located. I don't think you need to do anything with a computer module. All you need is to find the source of the wire running to the rear bumper. Probably either under the hood or under the dash.

 

These later model trucks have a "Body Control Module" that runs a number of things, one being the lighting. It's under the hood on the passenger side.

If I understand what you've posted correctly, I could take a relay and install it so that with the upfitter switch in the off position the trailer lights operate normally and with the switch on the trailer lights are off allowing me to flash the lights.

 

Correct. Very simple project.

 

I can't thank you guys enough for all the info on this thread. I had a general idea where the wires from the upfitter switches might be but the underdash area is just a jungle. Knothole...your photo saved me a whole lot of time and aggravation. It made my day. I located the wires in about 30 seconds. Thanks again!!!

 

I am looking to add some Rigid D2 fog lights to my 2013 F250. I want to run them off one of my uplifter switches.
I guess the uplifter switches already have relays built in. These lights come with a relay harness as well. How should I go about wiring these up to the uplifter switch without screwing something up?

I appreciate the help.

 

Ive got my trailer lights connected to my #1 upfitter for so that I can turn on my trailer marker lights independent of my truck lights and also say "thank you"

I intercepted circuit CBP30 (between the splice and the trailer tow relay), so now my upfitter powers up the trailer light relay. Note- I did not "T tap" into that wire. I cut and insulated the end going toward the BCM. I located that wire beneath the under-hood fuse block which requires removal of the driver's fender liner.

I also like it because it allows me to turn off the marker light function of my LED "line of fire" light bar, but also flash it when saying "thank you" without a trailer in tow.

If you would rather it be that when the upfitter is "on" it shuts the trailer lights off, you could always pass that circuit through a second relay to break the circuit.

 

Slowlearner, I really appreciate the post. I'm going to PM you to pick your brain a bit. This looks like the solution I've been looking for.

Thanks again,

 

Looking for guidance. I have a new 2012 F250 4WD with 6K miles and it does not have the upfitter switches in the dash. I have the factory trailer brake and beside the brake is a coin holder. The dealer parts department told me all I need to do is buy the switches and everything is there to connect in. I popped out the coin holder and I see no harness connector. How can I tell if my new truck has the harness already installed? I cannot find the relay assembly for the upfitter switches.

 

None of them have the harness or relays. All of them have the socket in the fuse block to connect the harness. Your dealer might have an option to sell you the switches, relays, and harness as a kit. You will have to ask them what they are including.

 

Hi, I have a 2012 f250 that came w/ upfitter switches. I was wondering if I wanted to hook up kc fog lights to the upfitter switch is it necessary to still ground the lights or do I just connect the harness to the switch?

 

Yes. For an electrical device to work, you must have a connection to voltate potential (the upfitter switch output wire) and a connection to ground (the trucks frame).

Be cautious of current draw of the lamps and the rating of the switch. You might need a relay. Frankly, if you have to ask that question, you might want to get someone knowledgable to help you. No offense intended.

 

I understand the concept of electrical work Bill and grounding wires, however some people on other forums tell me the upfitter switches are already grounded and it not necessary. I find it hard not to take offense to your reply, just wanted to ask around and see if anyone else has anything different to say.

 

DomB ...please take a deep breath and do not take offense to the reply - your question did seem to be an extremely basic one - only you know your level of expertise - it did not necessarily shine thru in your question - peace out

It's all about our trucks !