Hi Lexus enthusiasts,

I recently bought a 2013 Lexus RX450h F Sport with ~195 000km (121 000 miles) on the clock. The car is in good condition, it was advertised to have the HV battery replaced, but that turned out to be false. (another story how I decoded the serial number and manufacture date)
To the issue/problem:
When I test drove the car during a sunny day I did not see any problem with the heater, it was set on auto and it looked like it was doing its job. Bought the car, the weather got a little chilly and noticed a strange problem - when the car went to battery mode, either you are stopped on a light, stopping or just using the battery - it was blowing cold air out of the vents. I looked online and all the topics were saying low coolant or air in the coolant system. Coolant level seemed fine both in the radiator and in the expansion tank. Got it to the dealer, they told me that the car has a problem with the radiator cap and they suspect that there was air in the system. They bled the system, new cap was ordered and hot air was blowing in the parking lot and on the way home. The issue came back until the cap arrived in the dealership, they had another look, tried to bleed it again, but said that another longer diagnostic will be needed for the auxiliary electric heater pump(part no 06410-01080), which pumps the coolant through the heater core, when the ICE is off. I checked the pump with techstream and indeed, it was starting like 2 out of 5 times, so there was a problem there. Pump has been replaced in an indepndent shop with a used one (tested, working as expected) and now it seems that the situation is much better. However I'm not 100% sure, that this is how the system should behave, please check below my analysis with a thermometer on the central vent.

Outside temperature is 14C (57F)
Engine is at working temperature, the dial is perfectly at mid.
Blower set to face, TEMP HI, fan on 3.
Thermometer when the ICE is working shows 64C degrees (147F).
When I depress the pedal and the car goes to battery mode, the temperature is rapidly going down and it takes around 5 minutes to reach 30C (86F) which is kind of lukewarm and not hot at all.
If the blower speed is set on max, instead of 3, the 86F comes much faster.

So I'm here wondering if that's normal and that's just the way this heating system is working, as this auxiliary electric pump looks very small and probably cannot keep up with pumping so much coolant in order to keep >50C as a temperature.

Has anyone performed such a test or is willing to do one on a 3 Gen Hybrid RX?

I really like the car so far, but this is bothering me and not sure if it's normal.

Any feedback will be appreciated.

Borislav

 

Just a quick update on the issue, for sure the problem is not resolved.
Tested today on RX400h (which has absolutely the same pump and setup), thermometer was showing 75C (167F) when ICE was running, after the car went on battery, actually the temperature started going up at first, probably cause the coolant was not cooling the engine anymore as the main belt driven water pump is not running, but instead the auxiliary pump is now pumping coolant through the heat matrix witch much lower flow. Then it stayed at 70C+ degrees for quite some time and it was not dropping, but instead blowing VERY hot air in my face, as it should be.

On my R450h it's also showing 75C when ICE is running, whenever it turns off and the car is on battery, it drops to 35C (95F) for about 4 minutes.

My mechanic's suspicion is that either heater radiator, which is behind the dash is blocked partially somehow or the "new" pump is not working as expected, like the flow is not enough.

Still trying to figure this out. Otherwise the car is great and is a huge upgrade from my old Corolla.

Will keep updating the topic with ideas and hopefully the solution.

 

As promised, I'm updating the thread.

The vehicle got back to the dealer for a follow up diagnostic, where they said that some disassembling will be needed in order to test the pump and check the electrical connections.
During the diagnostic they did not do anything like that, there were couple of techs around the car for an hour tops, they ran some diagnostics, did not dissasemble anything and park the car in the garage, waiting for another tech to do an oil change, which was also scheduled.

I instantly asked what is going on and the answer was that the problem with the heating was resolved. How - they changed a fuse + "repair of the electrical installation" without any further information.

So, at the end I'm not sure if the pump was problematic in the first place, I have the old part, but not sure that will be able to test it out and honestly don't want to deal with that.

Now, it's blowing with more than 65C degrees while on battery and looks like it's working as expected.

 

We have a new to us 2013 RX450h, weather is getting a bit chilly, and my wife says the heater is not blowing hot air like our old RX300. Do you happen to know which fuse was replaced and the location of the fuse so I can check it? Thanks.

 

Unfortunately I have no idea which fuse was replaced or the location. It was done by the dealer, they also did a "repair of the electrical installation", whatever that means. I don't think that it was a big issue at all, the problem was that they were not able to do a good diagnostic on the first time.
I would check the radiator cap for sure - it's a weak place and might be problematic. If you have access to Techstream you can test the auxiliary pump, if it's working when you test it. It's again chilly weather right now ours is blowing very hot air even on battery.

Good luck with solving the issue!