S80 Rear Window Heating Issue

I had a similar problem with my S80. Does the light on the rear defroster button come on when you press it? In my case, it was a bad relay. Have you checked the fuses? Easy to rule out. If those are fine, have you tested the voltage at the rear window heating grid itself?

Thanks! The light on the defroster button does come on. I've checked the fuses, and they seem fine. I haven't checked the voltage at the grid itself yet - not sure how to do that safely. Is it easy to access the connector without damaging anything?

Okay, if the light's on and the fuses are good, and especially since you mention other electrical oddities, your hunch about the battery might be right. Testing the voltage at the grid can be fiddly. Given the symptoms, taking it to a reliable workshop might save you some grief. It could be the battery, but there are other potential gremlins.

Thanks! I took your advice and brought it to a shop. You were right; it ended up being a heavily discharged battery causing weirdness. New battery installed, and the rear window heating is working perfectly again. Cost me 290€, but worth it.