Just bought a 2010 RX450h w/ 80k miles and the heater is not great. Wondering if something is up with mine, or if it's typical for these cars.
I've closed the back seat vents, run the car for 20min, fans work, it just doesn't get very warm.

 

Hybrid cabin heat is not very good [key word very]. I use car seat heat option to improve environment.

My mpg also goes down when it is cold outside.

Salim

 

We have no issues with cabin heat in our 2014 RX450h ... and we see winter temperatures down to -32 C (-26 F). We also typically run our RX450h in ECO Mode.

See the statement below from our owners manual about possible heating issues in ECO Mode:

"Operation of the air conditioning system in Eco drive mode.

In Eco drive mode, the air conditioning system is controlled as follows to prioritize fuel efficiency:
●Engine speed and compressor operation controlled to restrict heating/cooling capacity
●Fan speed restricted when automatic mode is selected

To improve air conditioning performance, perform the following operations:
●Adjust the fan speed
●Turn off Eco drive mode
■Customization
The air conditioning control of Eco drive mode can be changed to the same setting as that used in normal drive mode. (Customizable features →P. 825)"

 

Thanks. I'll look in the settings to see if Eco mode might be affecting anything.

 

If you don't get increased heat by turning off the ECO mode, it might be the thermostat that is causing the problem.
From what I understand, it is a lot of work to change out a thermostat on a hybrid.

Have a look at this video ... it is on a 2007 Lexus RX400h ... not sure if it is the exact same procedure for your 2010 RX450h ... but I expect it to be similar.
Be sure to watch to the end of this video as the mechanic explains why he had to change the thermostat (starting at about 4 min 20 sec).

You Tube

 

And check out these other threads for cabin heat related concerns:

https://www.clublexus.com/forums/hyb...in-winter.html

https://www.clublexus.com/forums/hyb...is-normal.html

 

Thanks for the vid. That does look like a project! Might have to do some poking around to see if the 2010 is similar enough.

 

Turning off Eco mode didn't solve it. Maybe it is a thermostat thing. I timed it and it took 8 min the heat to even turn on, another 10 to start feeling lukewarm, and that was with freeway driving.

 

Please share how the temp gauge behaves when you start, after 5 minutes of driving and 15 minutes of driving?
Also if coolant was replaced shot while before observation of the poor heat.

Salim

 

Going to do more testing, but the fans didn't kick on until the temp gauge reached 1/4, which took about 8min. After another 10 min it reached about 3/8, then settled back to a little above 1/4. That was in the morning when it was colder. In the afternoon it reached 1/2 about the same time frame as it took to reach 3/8ths before. Will check coolant, but wouldn't low coolant mean more heat (not in a good way of course)?

 

Exact opposite. Its the coolant that carries the heat to the cabin. Low coolant, no heat to the cabin but the engine burns up.

And to answer your question, I've not had any issues with heat here in the Great White North. Maybe just because our idea of unbearable heat is 85F. -10F, meh, sometimes I just use the seat heaters, thats good enough

 

Coolant is ok, so I'll look at the thermostat.