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Heat on Driver's side but little heat on Passenger side

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Folks, our 2004 ES330 produces good heat on the driver's side.  On the passenger side, the heat is lukewarm at best.  AC runs cold on BOTH sides.

The most common failure is the heat/cold mix door motor.  That is working fine.  I can observe it in operation.  In the Heat mode, it moves the door lever into the proper position.  Likewise in the Cold mode.  It matches the movement on the driver's side.

The heater core appears to be working fine.  No leaks.  And on the Driver's side, the air with the engine warmed up is hot as it should be.  And both tubes to and from the core are hot to the touch.

Does anyone know if there is a temperature sensor somewhere which measures the difference between the two sides?  This is dual climate control so the driver and passenger sides can be controlled independently.

Or has anyone ever found another cause for this problem which is not related to the heater core or the mixer door operation?

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55 minutes ago, Lexus Owners Club said:

I wonder if a scan of the HVAC system would reveal a fault code to narrow down the possibilities.

If the Air Temp Sensor can easily be accessed then maybe swap them around to see if the fault transfers over

I've done the scan method (auto+recirc and turn on key) and it went through the cycle.  Only codes 21 and 24 shown up.  The car was in the garage at the time so naturally those codes would display.  No other codes were displayed.  Then the AC cycling through the modes 0 through 10 and no error codes showed up.

As for the Air Temp Sensor, I suppose  you're referring to the ambient temp sensor in the cab.  That's located under the driver's side dash.  I don't know of one on the passenger side.  Perhaps there is, and that would make sense.  

But, the actuator moves with mode and temp changes and no alarms are displayed.  It just seems that perhaps the blend door itself may not be fully closing for some reason.  I'm still looking for possible causes.


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  • 8 months later...

I still have not resolved the problem.  Though it is winter here, our drives around town have been mostly short and the car is kept in the garage so it's not that cold inside when we start out.  So it's not been a huge problem right now.  But the problem remains.  There is virtually no warm air coming out on the passenger side.  And I have verified that the passenger side blend door does operate fully in both directions in response to the heat control.

I have seen references to something called main mode panel actuator.  Looking at pictures of that device, it does not resemble at all either the left or right blend door actuators.  I can find zero information on what that is for or where it is located.  And the info on it in the ads all swear that it is for the 20004 ES330.

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