Smart Roadster Power Seat Fault: Wiring vs Switch Issue

Had a similar issue with my 2003 Smart ForTwo passenger seat. Got experience working on basic electrical systems but needed professional help with this one. The power seats stopped working completely and diagnostic showed a power supply issue. After checking the seat harness connections, the workshop found the root cause was a heavily discharged battery causing electrical system faults across multiple components, including the automotive seat controls. Complete fix involved: Battery load test and replacement, Testing all power seats circuits, Checking seat harness connections, Resetting error codes, Full system diagnostic Total repair cost was 290€ including parts and labor. Since then, no issues with the seat adjustments. To better assist with your specific case, could you share: Any other electrical issues happening at the same time? Does the driver side power seat still work normally? Are there any unusual sounds when trying to adjust the seat? Have you noticed any battery warning lights? These details would help determine if your issue matches what I experienced or points to a different problem with the seat controls.

Thanks for sharing your experience. My mileage just hit 141787 KM at last service, and I can confirm there are no other electrical problems happening. The driver side seat motor works perfectly fine, and I dont hear any unusual sounds when attempting seat adjustment on the passenger side. The seat harness looks intact from what I can see, but Im not able to properly test the connections. The passenger seat stays completely unresponsive, no movement, no noise, nothing when using the controls. No battery warning lights showing up on the dash either. Based on what youre saying about your repair, this seems like it might be a different issue since my battery is relatively new and other electrical systems are working normally. Did your workshop mention any other common failure points in the seat adjustment system that could cause complete loss of function on just one side?

Thanks for those extra details about your Smart Roadster seat issue. This does sound different from my battery-related case, especially since your other electrical systems are working fine. When my workshop did the repair, they mentioned several other common failure points specific to the passenger electric seat system: 1. The seat switch itself often fails due to internal wear, common after 100000 KM 2. Break in the wiring between the seat switch and motor 3. Faulty seat motor (though this usually makes grinding noises before failing) 4. Corroded connectors under the seat In my case, while the battery was the main culprit, they found moderate corrosion on the seat connectors during inspection. Worth checking since these connectors are exposed to moisture and dirt over time. Since your passenger seat shows zero response and no sounds, Id suspect either the power seat switch or a wiring break. The switch is usually the easier fix, typically costing around 150€ installed. A wiring issue could run higher depending on location and extent of damage. Before taking it to a shop, you might try checking if the seat fuse is blown, its a simple first step that sometimes gets overlooked. The complete silence from the seat adjustment system points strongly to an electrical supply issue to that specific component.

Good details about the seating issue in my Smart Roadster, really appreciate the thorough response. The mileage and symptoms do match what you described about the seat switch possibly failing after 100000 KM. Think Ill first check that fuse you mentioned since its an easy first step. My next service is coming up in a few weeks anyway, so if the fuse looks good, Ill have them diagnose whether its the power seat switch or wiring. The 150€ estimate for the switch replacement seems reasonable if thats what it turns out to be. At least the driver side electric seat is still working normally, so Im not completely stuck with manual adjustments. Quick follow-up, would there be any visible signs if its the switch rather than deeper seat wiring issues? Just wondering if theres anything obvious I should look for when I check the fuse. Thanks again for walking me through the common failure points on these seat adjustment systems.