If your wiring is hooked up backwards it can cause serious damage to your vehicle, and possibly harm you! Not too long ago we had a customer call us after her 2006 Dodge 2500 truck starting smoking when she hooked up her trailer. After a little investigation we found the wiring to the trailer battery was hooked up backwards. One easy mistake can cause several thousands of dollars in damage!
The entire wiring harness removed from the truck- front end on left side.
When the battery was replaced the wires to the trailer plug were re-installed backwards. This ground out the plug and shorted the wires. The wires got extremely hot and melted down part of the fender.
The entire main wire harness had to be removed and replaced- that's no little task! The steering wheel, fender (obviously) and gas tank even had to be removed to gain access to areas the harness tied into the truck.