Heating System And Transmission

[rebb]

I have an RX 350 with Navi and only 44,000 miles I am unable to effectively maintain heating temperature in this car.

It reaches the set temp but then after a while, it starts blowing cooler air and never readjusts to the original temperature setting.

I have to keep raising it to well in the upper 80's to get it warm.

Also, when I turn it to the off setting, it still blows air through the center vents. Lexus says to put it on recirculating setting.

For me, "off" should mean off as in no air coming out of the vents. Anyone else have this problem and if so, is there a solution?

Regarding the transmission, the shift into third gear seems sloppy. It slides into gear with a hesitation. Again, Lexus says they can't find anything wrong.

[lenore]

That is not right, Why isnt Lexus addressing the problem? When we turn ours off, it is off...

[jaswood]

Heating wise you are encountering an anomally, I would say design FLAW, of the Lexus cliamte control design. More correctly a design flaw of the system designed and produced by NipponDenso for the majority of asian manufactured vehicles, and by Denso US fro a goodly portion of US manufacturers.

The base "fly in the ointment" is that in cool or cold climates and in fully automatic mode as the cabin temperature rises to, or closely nearby, your temperature setpoint the system will automatically switch into "cooling" mode, system airflow outlet at the dash level. That airflow, by design, will now be as much as 20F cooler that what was previously the temperature level from the footwell, floor outlets. If the OAT, or cabin inlet (recirculate mode) airflow entering the system is warm enough, above ~45F for OAT (recirc inlet will certainly be), then a substantual level of dehumidification will result. So now you have not only "cool" airflow directed to your face and upper body, that "cool" airflow is also quite DRY.

Net effect for the Human Comfort Equation, you "feel" chilled.

Yet another adverse effect is that if left to itsself, left in this "cooling" mode, there is NO warming airflow to the interior surface of the windshield in order to keep its surface temperature well above dewpoint. DANGEROUS that...!

Why...??

Idiot NipponDenso engineers would be my best guess.

But help is on the way.

The first thing you should do, at least initially, is to ALWAYS manually switch the system to footwell/floor, or BACK into this mode once it switches to dash outlet mode at a time when HEATING is desireable.

As of '01 there was 2 C-BEST options added. 1.) You can have the dealer set these so the A/C can be disabled indefinitely, throughout multiple ignition power on/off cycles. 2.) The dealer can set a 2nd option such that the A/C will be unlinked from operating automatically (with no indication to the driver) in defrost/defog/demist modes.

This will prevent the COOLING of the system airflow when the human comfort equation dictates HEAT as a requirement.

Later models, ceratinly beyond my '01, have an additional C-BEST option wherein the system can be prevented for automatically switching into "dash"/COOLING, airflow mode.

Another aspect, corrective aspect, FIX, later added to these systems is the ability (REQUIREMENT) to automatically switch into fresh inlet airflow mode AND automatically switch in windshield/floor "HEATING" mode once the is already, or OAT declines, below about 34F.

Since otherwise, absent your intervention as above or the application of these newer "FIXES", these systems will steadfastly remain in "cooling" mode. ABSOLUTELY NO warming airflow to the interior surface of the windshield and thereby becoming subject to the HAZARDS of sudden unexpected fogging, DENSE fogging of the windshield interior surface.

For more info see:

http://us.lexusownersclub.com/forums/index.php?showtopic=72410

[jaswood]

That is not right, Why isnt Lexus addressing the problem? When we turn ours off, it is off...

Forward motion of the vehicle will always slightly pressurize the atmosphere near the bottom of the windshield thereby FORCING airflow through the HVAC system. Since you DO NOT wish to have the system in recirc mode(***) during cool/cold weather operation the best you can do is set the temperature to MAX heating, select the defrost/defog/demist mode, and then switch the system completely off.

Reversing the direction of the incoming airflow in this manner will tend to "baffle" the level of incoming airflow volume while also directing it away from your face/body/feet. It will also serve, at the same time, to keep the interior surface of the windshield warmed to well about the dewpoint of the cabin atmosphere.

If the resulting airflow "reflected" off the windshield becomes to warm for comfort the temperature can be easily lowered as is obvious.

*** some systems will not remain in reciculate mode even with the system off, many will even automatically switch to fresh as you turn off the system, some will even also automatically direct the incoming airflow to the windshield routing with the system switched off.

If you check the condition, STATE, of the airflow routing upon startup on a cold morning prior to the coolant being warm enough for the heater blower to start, odds are, 100:1, you will discover it to be parked in the windshield airflow mode.

[jaswood]

I have an RX 350 with Navi and only 44,000 miles I am unable to effectively maintain heating temperature in this car.

It reaches the set temp but then after a while, it starts blowing cooler air and never readjusts to the original temperature setting.

I have to keep raising it to well in the upper 80's to get it warm.

Also, when I turn it to the off setting, it still blows air through the center vents. Lexus says to put it on recirculating setting.

For me, "off" should mean off as in no air coming out of the vents. Anyone else have this problem and if so, is there a solution?

Regarding the transmission, the shift into third gear seems sloppy. It slides into gear with a hesitation. Again, Lexus says they can't find anything wrong.

As of the RX330 Lexus adopted the DBW, e-throttle system, to "protect the drive train". With the advent of the use of a more FE appropriate transaxle design with the original RX MY Lexus found that the transaxle gear change timing did not always match up with the driver's need, desire, for quick acceleration. DBW adoption allowed the engineers to prevent the throttle from responding to accelerator depression unless/until the currently commanded gear change was fully complete.

That effect may be what you are encountering orif it is most noticeable during coastdown periods it might even be the full fuel cut technique effects that you "feel".