I have owned my 2008 Rx 400 h for just over two months now and at the risk of sounding dense, am I right in assuming that when you are coasting along without the engine running, the heater will start to blow cold air? Everything works fine until you lift your foot off the pedal. This is my first Lexus/Toyota and hybrid so I'm not totally au fait with how it should be working.
Any input would be greatly appreciated.

 

The heater always works in our 400h.

 

The temperature setting dictates the air discharge temperature to the cabin, if set on AUTO.

The sensor is located just below the steering wheel where return air sucked in. The temperature of the discharge air is normally hotter that set temperature when heat is called for and colder when cooling is required. The target is a mixed temperature between new air going into the cabin and return air, which is equal to your setting. Then the outside air temperature (and humidity) plays a major role as well.

I know because I have experience in air-conditioning, commercial and industrial.