VW Touran Window Heater Failure: Both Front & Rear Dead

I had a similar auto defrost problem with my 2017 VW Tiguan last winter. As someone with moderate car repair experience, I initially thought it was just a fuse issue, but it turned out to be more complex. The heating issue symptoms were identical, both front and rear window defroster systems stopped working, with warning lights on the dashboard. The thermal window system was completely unresponsive, much like what you are describing. After a thorough diagnostic at my regular workshop, they found the root cause was a heavily discharged battery that was no longer holding proper charge. This was affecting multiple electrical systems, including the defroster repair components. The total repair cost was 290€, which included a new battery and system testing. Before suggesting specific solutions, could you provide: Current battery age, Whether you notice any other electrical issues, If the car has been sitting unused for extended periods, Whether you see dimming lights when using other electrical components This information would help determine if your Touran is experiencing the same battery-related heating issue as my Tiguan did. Have you checked if the battery warning light comes on when starting the car? This could confirm whether we are dealing with a similar situation.

My car had its latest service at 15000km and is running smoothly except for this defroster problem. After reading your detailed response, I checked and noticed the battery warning light does flicker briefly during cold starts. Testing with a multimeter shows the battery is only holding 11.8V when the car is off. I am now seeing slight dimming of the interior lights when using multiple electrical features. This does point toward the battery being the likely culprit affecting the car defrost systems rather than individual thermal window components failing. Will get the battery tested properly to confirm, but this explanation makes a lot of sense given the symptoms. Would rather sort out a simple battery replacement than face extensive defroster repair work.

Thanks for the voltage readings and update. Those battery symptoms match exactly what I experienced with my Tiguan last winter. The 11.8V reading is definitely too low, a healthy battery should show around 12.6V when the engine is off. The flickering warning light and dimming interior lights, combined with both window heater functions failing, strongly indicate a failing battery situation just like in my case. The car defrost system needs proper voltage to function correctly. While its tempting to just replace the battery, I would suggest getting a proper diagnostic check first. My auto defrost problems were fixed with a new battery, but the workshop also found slight wear on some electrical connectors that needed cleaning. The total job cost around 290€ including labor, but prevented potential future window heating failures. The good news is that window demister system components themselves are likely fine, once you restore proper battery voltage, the thermal window functions should return to normal operation. Modern cars are quite sensitive to voltage fluctuations when it comes to electrical features like the window heater. Would recommend not waiting too long to get this checked, as continuing to run with a weak battery can potentially affect other electrical systems beyond just the car defrost functions.

Thanks for confirming all those details regarding the battery situation. The voltage readings explain why my rear window and front defroster systems have been acting up. The 11.8V reading definitely indicates a weak battery, which would cause these heating coil issues. The similarities between your Tiguan case and my Touran problems are quite striking. I will book the car in for a proper diagnostic check rather than just assuming a simple battery swap will fix the auto defrost completely. Makes sense to check those electrical connections too while they are at it. Good to know the thermal window components themselves are likely fine. The 290€ repair cost seems reasonable if it resolves both the battery and prevents future defroster repair issues. Will get this sorted soon before the weak battery starts affecting other systems. Really appreciate you sharing your experience, helped me understand what is actually happening with my car defrost problems rather than just guessing at the cause.