I am really late to this party, but I am having this issue with my LS600hL. On days below 30 degrees, I really notice the car not blowing hot air while engine is off and car is on hybrid power only. If I sit idle and the gas engine shuts off, I will be in the cold no doubt. Once I start driving again, it comes back. I have an appt this week, but perhaps I am dealing with an air lock issue also. Thanks for this thread, it was helpful!