tonyhui

Has anyone with the new RX450h experienced a lack of heat in the cabin when the temp/fan is set to Auto? Recently when the temperature was -7C/19.5F I had to drive 20 minutes before there were any heat from the vent and it took another 10 minutes before the auto setting provide full blast of hot air. The dealer tested the car and couldn't find any problem. I had four previous cars that have auto control (including the last generation Rx400h) and non of them hehaved this way. Here is my observation: The fan stayed off until the temperature gauge reached about two markings then it go to the LO fan speed. The fan go up one speed when the temperature gauge reached 3 marks. Only when the temperature gauge reached 4 or 4.5 will the auto fan speed moved to HI. The problem is when the temperature is cold and when travelling in slow city traffic, the engine shut off regularly after only two marks on the temp gauge so no heat in the cabin. I would appreciate any comment on other users' experience. Thanks.

Cruiter

Seeing that you live in Canada, I only presume your temps are several degrees lower than ours. I don't know, but maybe it's cold enough that your car is working as it should. If you have the seat heaters that should help. If you waste a little gas for the sake of heat and accelerate just a little harder that might warm the engine up a little faster too. But in theory all things being the same, it should warm up faster than your 400h did because of the Atkinson system.

If you have the NAV system, go into setup and make sure nothing is turned off on the system. Ya never know what might need re-setting. Good luck.

RXSF

why not just take it off auto and set a desired temperature with desired fan speed? I didnt know that the fan speed was correlated to the engine temperature. Are you on ECO mode?

DaRacerz

One detail I have noticed in my limited testing, see if you are operating in ECO Mode = On. If so, switch it off and see if the warm up time decreases and hopefully by a significant amount.

I have noticed that running in Eco Mode, the Engine is Warmed up on Idle rather than in gear and tends to shut off more often, causing the Heater to take longer to heat up the cabin. Taking of Eco Engines seem to run in gear and also not shut off at the lights giving you more heat faster.

Haven't paid attention yet when the fans turn on in relation to the temperature gauge, but i'll pay attention on the next drive.

PatsSoxfan

The Eco Mode is indeed the culprit for this "problem". My dealer mentioned this to me a week ago when I brought my LS in to reset the tire pressure monitor. I was conversing with a salesman and he asked me how the RX450h was doing. He then told me on his own (since we have not really noticed a cabin heating problem) that if we have trouble getting the cabin temperature warm enough, take it out of the Eco Mode.

tonyhui

Thanks everyone. The ECO mode was indeed the problem. With ECO mode on the temperature gauge barely moved before the engine shut off. After reading your posts I turned off ECO mode and now the engine continue to run until sufficient heat is blowing before shutting off. If the service department of my dealer is as knowledgeable as you guys they wouldn't have need to give me a loaner for two days while scratching their heads trying to figure out what was wrong. They even muck around and changed the temperature calibration so that what used to be 23C now I have to set to 21C thinking that that will raise the auto temperature.

Stormforge

good info guys. i had a similar problem as tonyhui, and i have been driving around in ECO mode as well. i guess there's only one choice: either better fuel economy or staying warm.

Aptosuser

I'm coming several years late to this thread, but that's because I just got a 2010 450h a couple of weeks ago and tried using the heater for the first time today (we live in N. California) while on a road trip and couldn't feel much cabin heat. The car was in eco mode at the time. I switched off eco mode but I didn't feel much change, so I put it back into eco mode. Maybe I should've left eco mode off for the rest of the trip? I was pleased with our gas mileage at any rate. I got better than 28 mpg on the outbound leg and car is now averaging over 28 mpg since I got it (with barely 15k on the odometer).

DunWkg

Creature comfort overrides good gas mileage for me. Turn off ECO, turn off AUTO and crank up the heat

Watch your temperature gauge, if that needle isn't moving up as your engine warms, you won't get heat in the cabin. If the needle isn't moving up to mid way, you may have a problem.

kitlz

LOL, David! I turned ECO off a week and half ago to stave off frostbite. Even used remote start a few times. Bun warmers have been on for the past month. With a five mile commute, the cabin barely gets warm but ECO off makes a difference. And forget about gas mileage. Fingers and toes are worth more

One thing I'd add. Heat defaults to the floor vents in auto. Press the mode button on the dash to switch to upper vents. Auto will turn off but it'll keep pumping out air at the temperature you selected versus maintaining the temperature.

Aptosuser

Last night I referred to the instructional DVD the dealer gave me with my Lexus. The whole time I was fiddling with the climate control -- while driving -- I was wondering if the A/C was on. It comes on automatically in our Camry hybrid and in my '07 RAV4 Limited whenever we turn on the auto climate control and in cold weather I always turn it off. Anyway, I didn't see a button to turn off the A/C in the Lexus. Per the DVD, it seems that you need to go into the climate menu on the NAV screen and turn the A/C off by pushing a virtual button there. I'll check later today to see if the air conditioning is on and if it is, I'll turn it off and see if that makes a difference. (Although I'm sure there must be experienced Lexuphiles out there who already know the answer.)

kitlz

Yes, the AC stays on despite the temperature. It's the default setting. I believe you have to go into the Menu screen, Setup, Vehicle, Vehicle Customization, Climate Settings to turn it off. I'm looking at page 408 in the nav manual. The 450h has to be turned on to make the change. To me it doesn't make a difference. And I'd rather have AC on in case the inside windows start fogging up in the rain.

DunWkg

Aptoduser, what was the outdoor air temperature when you thought the AC compressor was running? The manual says the "When outside air temperature is below 32°F (0°C) the cooling and dehumidification function may not operate even when [AC] is pressed."

This is what I understand is going on, hopefully someone more knowledgeable will step in and correct me. Temperature in the cabin is controlled by several variables: outdoor air temperature, sunlight (sensor on top of dashboard), smog sensor, position of all the switches (real and virtual), and the temperature (set point) you are requesting.

Let's start with a cold car, sitting outdoors when it is 30 degrees and the climate control system is in "Auto", the ventilation switch is in "Fresh", and you have the set point set at 74 degrees F. When you start the car, the climate control system will be in the heat mode, as ambient temperature is below set point and the cabin temperature (let's say 50 degrees F) is likely below set point. The climate control system appears not to be doing anything, no fan, no heat. In fact, it's waiting for the engine to produce some hot water. Your temperature gauge needle will be below the bottom tick mark. Slowly as the water temp rises to say the first tick mark, still nothing. As it passes the first tick mark, the fan may start on low. You don't want it blowing cold air. Slowly as the water temperature rises to to the second tick mark, the fan will be increasing speed too. The dampers controlling air flow have the heated air coming out the floor vents. Warm air rises so the whole cabin is slowly rising in temperature.

If the car is just sitting there, it may take 10 minutes to get the water temperature up into the "normal" operating range and as it does so the fan speed of the climate control system is at max or very nearly at max. It's still blowing air out the floor vents.

Slowly the cabin temperature is increasing and this temperature is sensed by a sensor located inside the dashboard. There's a little vent where cabin air enters and flows over the sensor to tell the climate control system what the temperature is in the cabin.

The air coming out of the vents is much warmer than the 74 degrees set point you have set in order to warm the 50 degree cabin up to 74. HOWEVER, all during this time the climate control system is also bringing in outdoor air to ventilate (provide fresh air and eliminate all the carbon dioxide you are exhaling). The system is heating, ventilating and circulating.

Okay, you are merrily traveling down the road, water temperature is in the "normal" range, cabin temperature is 74 maybe 75 degrees and now the climate control system enters the circulation/ventilation mode and the flow of heat decreases (to prevent overheating the cabin) and the computer controlled dampers change the air flow from the floor vents to the vents in the dashboard. Now air that is probably about 74 degrees is blowing in your face. It will feel cool. Air flowing over human skin feels cooler than it actually is due to "wind chill effect", even if you are not outside.

The computer will monitor cabin temperature and the set point you set and modulate dampers and the flow of heat into the cabin in an attempt to maintain set point (74 degrees).

None of discussion applies, if there is smog, any of the myriad of switches are not set automatic or the system is set in dual. Also the AC switch, in my mind, is an enable switch. If OFF the air conditioning compressor can not run. If ON, the air conditioning compressor is enabled. It is able to run if the climate control system is calling for mechanical cooling or defrost. ON does not mean it is on and running. It's a variable speed compressor and is enabled or allowed to run if that AC switch is ON. So AC does not run all the time that switch is set to ON.

Aptosuser

David, that is the best explanation I've seen re. how the climate control system works. I will run outside immediately and turn the A/C back on. It's a good day to run outside here (Santa Cruz, Calif.), because the sun is shining and it feels like 70 degrees because, well, it is 70 degrees right now. When I turned on the climate control the other day we were enroute home from just north of Santa Rosa where we'd gone for a family Thanksgiving gathering. The outside temp. at that point was maybe in the low 50s. But the day was clear and we were getting a lot of sunlight through the windows, so perhaps the car thought we didn't need much in the way of cabin heat then. I'd expected the fan to start up and it didn't. Now I guess I understand why. Anyway, if we still feel chilled when the car thinks we shouldn't be, we always have those wonderful seat heaters to fall back on, as it were.

We rarely see daytime temperatures drop into the 30s where we live. Around here, people complain about cold weather if the mercury falls into the mid-40s. But I grew up in Chicago (and went to college in Iowa) and I know what truly cold is. And I'll never forget it, either.

Steve