To troubleshoot a rear wiper issue, you need to consult the owner's manual for the fuse box diagrams (there are usually several fuse boxes in the vehicle). The rear wiper likely has a fuse in one box and a relay in another, or the relay might be integrated into a control module.
Steps to take:
1. Consult your owner's manual: This is the absolute first step. The manual will show you the location of all fuse boxes and which fuses control what circuits. Look for fuses related to the rear wiper, rear window washer, or possibly even the power windows (as those circuits sometimes share elements).
2. Check the fuses: Carefully inspect each fuse listed as potentially related to the rear wiper in your owner's manual. Look for blown fuses (broken filament).
3. Check the relays: Your owner's manual *might* show you the location of the relay boxes, but this information is less common than fuse box diagrams. Look for relays related to the rear wiper (if indicated). Relays often click when activated; listen near the fuse boxes when you turn on the rear wiper to see if any relays are clicking.
4. Wiring harness inspection (advanced): If fuses and relays are fine, you'll likely need to consult a Volvo wiring diagram (available online through various Volvo enthusiast forums or repair manuals). This will allow you to trace the wiring harness from the switch to the motor and check for breaks or shorts. This is not recommended unless you are comfortable working with automotive electrical systems.
In short: There's no single answer without your owner's manual. Start there, and be methodical in your checks. If you're not comfortable with electrical work, take it to a mechanic.
