I wanted to do the same thing, I have a power lifting light bar, and I wanted to be able to control it with the built in upfitter switches. In my case I am using the bar to lift and lay down antennas, not lights. The goal is that with the antennas layed down the tallest part of the truck is still the stock AM/FM radio antenna. Hey, when you crawl the mall sometimes you have to park in a parking garage, or I might need to super size a meal, or grab a nitro cold brew decaf double latte mocha triple shot at a drive through....or something.
Antennas up:
Antennas down:
In my case, the linear actuator for the power light bar has two inputs, a + and a -. The wires are red and black, but that does not matter. To drive the bar up you must provide + 12 VDC to the + input (red wire in my case) and chassis ground to the - input (black wire in my case). To drive it down you reverse that, and provide chassis ground to the + input and +12 VDC to the - input.
The upfitter switches provide + 12 VDC. But there is no way, without some kind of interface circuit, to turn that into controllable + and - inputs. Fortunately, that is a simple circuit, using relay/s, as has already been mentioned.
This simple circuit can be set up using a single DPDT (Double Pole, Double Throw) relay, or using a pair of SPDT (Single Pole, Double Throw) relays. I chose to do it with a pair of SPDT relays.
I chose the SPDT route because the relays are easy to find and very inexpensive, even for good brand named ones, and also I found a nice multi relay box that looked very at home under the hood.
Not this exact one, but like this:
https://www.amazon.com/gp/product/B076HJ4VN2/?tag=fordraptorforum-20
This is what it looks like installed under the hood. Driver side fender, behind the air box.
And here it is with the two relays installed, room left to drive a few other accessories with relays here.
Below is the circuit I used. AUX 1 and AUX 2 are two of the upfitter switches. You use one switch at a time, one of them drives up, the other drives down. To drive the bar up I turn on AUX 1 switch. To drive the bar down I turn on AUX 2 switch. You turn off either switch after the bar gets to the position you want it to be in. You can stop the bar anyplace between full up and full down by just turning off the switch you have selected. It takes under 10 seconds to go from all the way up or down to the other extreme.
The design is fail safe, accidentally turning on both switches will do no damage, in this case it will drive the bar to the up position. If one or both of the relays fails you can still drive the bar down using AUX 2.
You could do it with a single relay, a DPDT. As I said before, I chose to do it via two relays instead, but that was personal preference. It could be argued the single relay approach would be the more reliable as there is only one relay to fail.
Below is a schematic for a single relay:
T!
