Why does only one wiper work on my Ford Transit?

The Transit Custom and MK8 do not use a shared windscreen wiper linkage. Each wiper has its own motor, and the driver's-side motor is the master unit that controls the passenger-side motor through the LIN bus. This means that when the passenger wiper stops working, the most likely cause is often the motor or connector on the driver's side. A typical scenario confirmed on owners' forums is water entering the driver's motor plug, corroding or breaking its pins and preventing the control signal from reaching the other side.

What should you check before buying a new wiper motor?

Start by disconnecting and inspecting the plug on the driver's-side motor. Corroded or broken pins are the most common finding. Also check the washer pump: when it fails internally, water can travel along the wiring loom to the motor connector and cause the same fault. If the plug is clean but there is no signal on the control wire, replace the master, driver's-side motor. Take care when ordering because the motors have many different code variants. Match the number on the identification label, as a unit from another model year may not work at all. After installation, protect the connector against further moisture ingress.