We own a 2012 ford f550 6.7 powerstroke rollback tow truck and we r having issues with the parking lights only. We have headlights and dash lights just no parking lights. When we turn the switch on u can hear the clicking of the relay no fuses blown but no power to fuse #30 and 40 inside fuse box.. if we hook a jumper wire up to either fuse they will come one. Or if we sit and repeatedly turn the switch on n off they will come on but if u switch it to headlights they will flicker or go out. Ive replaced the switch and that isnt the problem.. we have checked all the battery cables and cleaned and fixed all cables on both batteries.. we have checked all plugs and cleaned them. The only thing we havent got finished is the taillights blinkers etc hooked up in the back as we had to add a new bracket or lightbar for those lights so we had to cut the wiring. Added new lights and fixed all wiring back there with new wires.. i run 2 junction boxes right now one up in front of the rollback and one in the back. Also have a whelen light bar on top and backup lights but never had a issue until we put the new light bar on the back. The only other thing is i added another panel of round lights on the body and i put a battery charger on one battery the day i hooked up the round panel of lights on the body because the truck was dead. Now the backup lights and light bar and whelen light bar are all on uplifter switches. The only thing i can think of is maybe because the taillights arent hooked up yet its never been a issue before when i rewired it couple yrs ago. Any suggestions would b great this truck and the wiring has been a mess from.the very start we are the second owner so didnt wire it from the start and it was a nitemare never mind the truck itself.