G35 Heat/AC Failure: Defog Sensor Problem?

Hey there! I had a somewhat similar issue with my 2003 Infiniti M45 (I have some experience working on cars, mostly basic maintenance). The symptoms you're describing sound really familiar. For me, it turned out to be a faulty cable connection that was messing with both the HVAC and mirror systems. Took it to my regular workshop, and they traced it to some corroded wiring connections. The fix wasn't too complicated they had to replace some cables and clean up the connection points. Cost me about 155 Euro, and everything's been working perfectly since then. What's your G's mileage, and have you noticed any other electrical issues? This info would help me give you more specific advice based on my experience.

Thanks for sharing your experience! Mine's at 68472 KM and had its last service about two months ago. I haven't noticed any other electrical issues, which makes it even more puzzling. Did your mechanic mention if this is a common problem with Infinitis? I'm thinking about taking it to the dealership, but I'd rather avoid their prices if it's something relatively simple like in your case. Good to know it might just be a wiring issue rather than something more serious with the sensor itself.

Hey again! Yeah, I definitely get why you're hesitant about dealership prices they can be pretty steep. When I talked more with my mechanic about my M45's issue, he mentioned that these wiring problems are actually pretty common in Infinitis from that era, especially in the HVAC system. Since your mileage is relatively low at 68K, it might even be a simpler fix than mine was. Looking back at my experience, I'm glad I didn't jump straight to replacing the defogging sensor. That would've been way more expensive, and it turned out the sensor itself was totally fine. The corroded wiring was causing all sorts of weird symptoms that made it seem like a sensor issue at first. Quick tip before you take it in, you might want to check if you can hear any unusual clicking sounds from behind the dash when you switch between heating and cooling. That was something I noticed in my car, and it helped the mechanic narrow down the problem area faster. A regular workshop should be able to handle this, honestly. Just make sure they have experience with Infinitis. Keep us posted on what you find out I'm curious if it turns out to be the same issue as mine!

Thanks so much for all the detailed info! You've actually made me feel a lot better about this whole situation. I just checked for that clicking sound you mentioned, and yeah, I can hear something when switching between modes. I'll definitely try a local workshop first instead of the dealership found one nearby that specializes in Japanese cars. It's super helpful knowing that these wiring issues are common in older Infinitis. Really appreciate you taking the time to share your experience and tips. I'll be getting it checked out next week and will update the thread once I know what's actually going on. Fingers crossed it's just a wiring issue like yours was!