We install LED Lights on customers trucks and now have 5 2014 Super Duties with lights on upfitter switches working just fine. OK, we installed on a customers 2014 F350 a 20" Rigid led light bar connected to upfitter #1 using supplied relay from rigid and triggering relay with upfitter. Two rigid spots on upfitter #2 (5amps) and interior bed leds (low amps) on upfitter #3. Truck died (ing. kill) on highway while towing 44' trailer and would not restart. Towed to dealer and they could not find anything. Then the truck would occasionally and inconveniently not start. This went on for weeks and customer not happy with ford plus they could not find anything wrong because no codes were showing up. Ford engineer comes in an points his little young inexperienced fingers at the led lights on the upfitter switches. Dealer disconnected upfitter wires and then Mr. Murphy's Law shows up, truck starts every time. Service manager is on my side saying no way this is problem. Engineer is saying they have seen something similar on tow trucks and ambulances but offered no solution or suggestions. In this day and age we will not touch a factory wiring harness to connect anything. Ford was nice enough to offer the upfitter package but to cause the truck not to start????? Anyone else seen this.