VW T-Cross Thermal Window System Failure Alert

I had a very similar issue with my 2018 VW T-Roc. With some experience working on VWs, I can tell you this heating issue turned out to be battery-related. Initially, I thought the heating coil in the rear defroster was faulty, but when the workshop tested it, they found the battery was heavily discharged and not providing enough power to operate the window demister systems properly. The error code was actually warning about insufficient voltage rather than a direct heating system failure. The workshop performed a complete electrical diagnosis and found the original battery had degraded significantly. After replacing the battery and checking all connections, both the front and rear window heating systems worked perfectly again. Total cost was 290€ including diagnostics, new battery, and labor. Before suggesting this is definitely your issue too, could you share: Does your battery warning light show on the dashboard? Are there any other electrical issues like dim lights or slow starter? How old is your current battery? Does the problem occur more frequently when the engine is cold? This information would help determine if your situation matches what I experienced with my T-Roc.

Checked my service record, last maintenance was just 2 months ago at 16097km and the problem started right after. My battery warning light is not on and the starter works fine. Battery is original from 2020. The auto defrost and rear window heating dont work at all, regardless of engine temperature. And yes, all electrical systems including lights work normally. Interestingly, I noticed the thermal window heating makes a slight buzzing sound when activated, but no actual heating happens. The error code appears immediately when pressing either the front or rear window defrost buttons. Wondering if this points more toward a relay or fuse issue rather than the battery?

Thanks for those additional details. Based on what you described, this sounds different from my battery-related issue on my T-Roc. The buzzing sound when activating the car defrost system, combined with no actual heating effect, strongly suggests a relay problem. Since both your front and rear window heater functions are affected simultaneously and the issue started after maintenance, I suspect either: 1. A defective heating system relay 2. A loose connection in the main power supply to the window heating circuits 3. A blown main fuse for the heating system In my case, before discovering it was the battery, we initially checked these components because the symptoms were similar. However, your fully functional electrical system and the timing with recent maintenance make me lean toward a connection issue. The best approach would be to: 1. Check the main fuse for the window demister system 2. Have the relay tested 3. Inspect all connections that might have been disturbed during maintenance Since this started right after service, you might want to return to the workshop as this could be related to the recent work performed. The repair should be considerably less expensive than my battery replacement was. Have you noticed if the buzzing sound comes from a specific area under the dashboard?

Thanks for the detailed analysis. I checked underneath the dashboard area and the buzzing definitely comes from the driver's side, near the fuse box. The window heater makes the same buzzing noise whether I activate the front windshield or rear window defrost. After your explanation, I agree this seems more like a relay or connection problem, especially since it started right after the service visit. I pulled out my manual and checked the fuse diagram, there's a specific 30A fuse for the thermal window heating system. Will check that first before heading back to the workshop. If the fuse looks good, I'll have them inspect the relay and connections that might have been disturbed during maintenance. Really appreciate the help narrowing this down. Will update once I know what exactly caused the window demister malfunction. Much better to start with these simple checks than getting charged for unnecessary diagnostics.