940 towbar pre-wiring – connections

Many 940 models have a ready-made connector (D5) that simplifies the towbar electrical installation considerably. You don't have to scavenge power from the tail lights; instead, you can connect the wires directly to this connector.

The connector is found behind the trim panel on the left side of the trunk, often near the fender or antenna base. It is usually a multipin gray or white connector.

Volvo wire color / Function / 7-pin socket pin / Standard color (trailer) White / Ground (GND) / 3 / White Green-Red / Brake light / 6 / Red Green / Left turn signal / 1 / Yellow Blue / Right turn signal / 4 / Green White-Green / Left tail light / 7 / Black Yellow-White / Right tail light / 5 / Brown Red / Rear fog light / 2 / Blue

If you want to make the connection neatly without cutting wires, you can buy 0.8 mm / 2.8 mm male terminals (e.g., from Partco or electronics stores). These are the same terminals commonly used in car stereos (ISO connectors). Crimping pliers: For these small terminals, F-crimper type pliers work best (e.g., Motonet or Biltema "uninsulated terminal crimpers"). If you don't have pliers, careful crimping with needle-nose pliers and light soldering ensures good contact.

Volvo's pre-wiring has two very useful "extra" wires that are generally not needed for a trailer: Continuous +12V: A thicker red wire that provides power even when the car is off (e.g., car cooler). +12V behind ignition switch: Useful for auxiliary devices you want to turn off when the key is removed.

Light fault monitor: The 940 has a strict light fault monitor. By using this ready-made socket you usually avoid unnecessary fault light alerts, as it is designed to account for the trailer load. Ground: Make sure the white ground wire is securely connected to the car's frame. Poor grounding is the cause of 90% of trailer light malfunctions (e.g., turn signals dimming when brake is applied). Protection: Use heat-shrink tubing and protective sheathing on the wiring harness under the car so road salt and mud don't corrode the connections.