Several different problems may cause your car's rear windshield wiper to not work properly. Rear windshield wipers commonly receive less attention and maintenance than front windshield wipers, because we do not drive our cars down the road in reverse, making it less of an issue. However, your rear wiper can be very helpful in removing snow and frost from your car during winter months.
If your rear wiper seems to be smearing the water rather than cleaning or wiping it away, chances are you need a new wiper blade. Just like front windshield wipers, your rear blade will wear out over time and need to be replaced to achieve maximum wiping effects.
If your rear windshield wiper is not traveling smoothly across your rear windshield, it may be getting stuck or hanging up on something. Check to see if there is anything in the windshield wiper arms path that might stop it from properly functioning. Stickers or decals on the back windshield are a common culprit.
Your windshield wipers have more components than you might think. The wiper motor controls the actual wiper arm, but there are also wiring and switches that can experience shorts and cause the wiper to function at its own discretion, rather than when you tell it to. You may also have a blown or malfunctioning fuse that is stopping your wiper from working or transmitting signals inconsistently.
Windshield wipers motors have park circuits in them. If your rear wiper or wipers are stopping wherever they want to, rather than in the down position, chances are the park circuit isn't working properly.
