Hooked trailer wiring to my Tourer. Trailer plugged up, no blinkers, Bike running light off while trailer running light on, Brake light working normal. Unplug and bike lights return to normal. Note, I have an LED bulb in the rear. I found out rather abruptly that my single bulb blew. Without it nobody can see you.
You will have nothing but problems with your lights.
I have already been thru it with my trailer lights and I found out the hard way that you need a power module.
You need this and your lights will be fine. Information on Modulites
Followup. Hooked a Timeout Camper to my ride. Break lights were constantly on. Found out the 1157 LED bulb I put in the tail light caused 7 volts to be constantly on. It was enough to tell the break relay to turn the break lights on. Went back to normal bulb. No issues.