When towing travel trailer both blinkers blink when right turn signal?

Answer 1

The condition you describe suggests that the wiring to or on the trailer was not done correctly. In the towing vehicle there are two separate conductors [wires], left and right, going from the turn signal control switch, one to each of the vehicle's rear turn signal bulbs. When a vehicle is "wired" for trailer lighting, a connector plug pigtail is tapped into the vehicle's tail light, brake light, and turn signal electrical wires. The pigtailed connector plug kit usually contains a color coded schematic diagram indicating which wires on the plug pigtail are to be connected to the vehicle's lighting system, and for the trailer harness. From the connector plug at the front of the trailer tongue, there are separate wires going to the left and to the right turn signal lamps or filaments. There is one of two circumstances causing the error responsible for both turn signal bulbs on the trailer to flash at the same time: 1. The wires in the vehicle pigtail are both connected to the same turn signal wire at the rear of the towing vehicle, or 2. The two separate wires in the trailer wiring harness, or pigtail, are somehow interconnected. The correction for this is to have someone, who knows what he/she is doing, to troubleshoot the connections at the rear of the towing vehicle and in the trailer wiring harness, locate the cause of the interconnect, and properly remove the fault.