Pretty easy task... Unplug your 7-way cable and either plug in a short jumper or flasher unit in pins 3 and 4.
This will connect your trailer battery to the side marker lights and either just turn them 'ON' or 'FLASH' as you want to do. Some folks will plug-in a 12VDC ATC BLADE FUSE in pins 3 and 4
You won't be a well liked camper doing this at night for very long time periods...
Its a great idea for when you have to call security or rescue squad. Just tell them its the trailer with flashing marker lights going...
Roy Ken
My Posts are IMHO based on my experiences - Words in CAPS does not mean I am shouting
Roy - Carolyn
RETIRED DOAF/DON/DOD/CONTR RADIO TECH (42yrs)
K9PHT (Since 1957) 146.52M
2010 F150, 5.4,3:73 Gears,SCab
2008 Starcraft 14RT EU2000i GEN
2005 Flagstaff 8528RESS