QuestionWe have a 94 Lexus that has been an excellent car with one difficulty. The heater won't blow hot air. Diagnostically the heat/ac is in fine. We have checked most everything, yet can't get hot air to blow. We have even stumped our local Lexus Service Manager. I am trying to locate a diagram or schematic to see the cable that operates the door that opens to allow heat in, but have not found it. The cable seems to be in working order, but since I've read through some of your answers, I'm wondering if it may be the motor that operates that door. Can you help me trouble shoot this, or if you have a different idea of what my problem could be, could you please share it?
Thanks so much!
AnswerIt could be.
It's really sort of simple. If the blower works, the divider between the heater core & A/C evaoprator operates, the coolant is hot coming out of the engine, the valve opens, and the heater core is not blocked - you get hot air.
Which Lexus do you have?
Run the engine until it's warm, then turn the heat on. If the hose as far back from the valve is as hot as infront of the valve -> then most likekly the valve is working. Same for the coolant line that returns coolant from the heater core. If it's seriously hot, then the heater core is most likely not seriously plugged.
Make sure that little valve is opening & the heater core isn't plugged.
90% of the time I run into either heater cores that are plugged from people not changing their coolant every other year, or the valve arm has broken off / the motor won't operate it. Get someone to turn your heat on & watch it operate. You can see it open. If it opens, then it's something else.
