I have a 1999 RX300 with 128,000 miles and for no known reason the heater has quit working. A/C works fine but no heat. Any ideas?

 

Pita- check what happens when you set the temp to HOT. If you get heat at HOT then it might be your air mix servos. I had the reverse problem where the AC didnt work unless I set to COLD. Once the air mix servo was replaced everything was ok.

 

No heat in summer? Here in central Texas, we just have to lower the window

I would also check the coolant level ... not just the level in overflow but in the radiator [with engine cold].

Salim
ps: I have moved these posts to a new thread as they had nothing to do with high-milage