BMW X5 Rear Window Defroster Failure, Fix Guide

Had the same issue with my 2005 BMW X3 last winter. Initially thought it was just the heating element, but turned out the battery was severely discharged and couldn't provide enough power to the rear defroster. At the garage, they ran a full diagnostic test which showed multiple voltage drops. The battery couldn't hold a proper charge anymore and was affecting other electrical systems too. Had the alternator tested as well, it was fine, but the battery needed replacement. The warning light issue you're describing matches what I experienced. It's a pretty serious problem that needs immediate attention since a failing battery can affect your car's entire electrical system, including critical components like the starter motor. Just throwing this out there, you might want to get the battery tested first before diving into rear window heating repairs. A simple voltage test could save you from replacing parts unnecessarily.

Thanks for sharing that! Definitely sounds similar to what I'm experiencing. That's good to know about the battery connection, wouldn't have thought of that. Mind if I ask how much the whole diagnostic and repair set you back? Also, have you had any other electrical gremlins pop up since getting it fixed?

Hey there! Just wanted to follow up on your questions. The whole thing with diagnostics and the new battery ended up costing me 290 €, which honestly wasn't as bad as I feared. And I've got good news, since getting it fixed, the rear window heating has been working perfectly! Actually, several other little electrical quirks I hadn't even noticed before cleared up too. The battery replacement really did the trick, no more electrical gremlins at all since then. It's amazing how one failing component can cause so many weird issues, right? My X3 is running like a champ now. If you do end up getting yours checked out, definitely have them look at the battery first, could save you a bunch of trouble hunting down other supposed problems. Seriously, it's been smooth sailing since the fix. Best money I've spent on the car in a while. Let me know if you end up getting yours sorted, curious to hear if you've got the same underlying issue!

Thanks for the detailed follow-up! You actually convinced me to bite the bullet and take my X5 to a mechanic yesterday. Funny enough, you were spot on, it was definitely a battery issue. The mechanic did a full diagnostic and showed me how the old battery was barely holding 40% of its charge. Got it replaced, and wow, what a difference! Not just the rear window heating, but even my power windows seem smoother now. The whole thing set me back about 320, including diagnostics, which wasn't too bad considering all the improvements. Really glad I asked here before trying to tackle the heating issue separately. Could've ended up spending way more chasing the wrong problem. My mechanic even mentioned how common this issue is with older BMWs, wish I'd known this sooner! Again, thanks for sharing your experience. Saved me from another frustrating round of trial and error with my old mechanic. Car's running great now, and that annoying warning light is finally gone!