2003 RX300 blowing cold air when heater is on

[2003RX300SE-L]

Hi all,

When I turned on the car heater the other day I noticed that only the front passenger side vent blows warmish air, the drivers side and rear vents blow cold air. I set both sides to max hot and still no difference. The air for the passenger side also wasn’t that warm, only warmish at best. I have noticed that the engine temperature seems to be on the low side. Even after driving the car for over 7 hours from London to Scotland the engine temperature guage dial was only at the one quarter position, i.e. between cold and midway. Surely after a long drive like that the temperature guage should have been sitting comfortably at the halfway mark?

Thanks all. 

[Baldguy]

Sounds like a thermostat issue you have there, stuck open or closed....

[m4rkw]

Simplest thing is to change the thermostat, I had this happen over xmas 2021. I think it was about £7 from Euros, much cheaper than a diagnosis and if it doesn't help then you haven't lost much. Very easy to change yourself but be very careful tightening it, you don't want to over-torque it and strip the threads in the engine block.

[2003RX300SE-L]

Thanks all