I have a feeling there's already a thread for this issue, but cannot find resolutions. I recently purchased a 2016 IS300 F Sport, and my heat suddenly stopped blowing hot air. Fans work, thermostat works, coolants full, a/c works and blows colder air. I've also hard reset the battery in case that solved it.

Any ideas before I take to Lexus for what they're calling a V4 Maintenance Service costing $449.95 plus tax!?

 

I recently had the opposite happen, trying to turn on cool but ended up getting hot air. Was driving and everything, even turning off the AC and letting in fresh air was hot. I even tried to turn on heat thinking it would flip to cold but it only heated up. When I finally was able to pull over, turned off the car and about two hours later, it worked correctly.

Don’t know if it was a glitch or something. Still don’t know what caused it. Hopefully it was a one time occurrence and it won’t happen again. How long did you disconnect the battery for? Maybe try longer?

 

I disconnected the battery for 15 mins, turned the ignition on without starting the car, I allowed the system to completely reset.

This seems to be a somewhat common issue with these cars, I'm used to Subaru's, still learning the quirks of Lexus.