'93 Sc400 I have replaced the thermostat and Heater Control Valve and I still cannot get anything but HOT HOT air to come out of the vent, even when the dial is set to 67 degrees (cold).

also worth mentioning is the fact that on cold mornings, the car will not blow hot air until i get going at a high RPM( High way speed. I can let the car idle in my driveway for 15-20 minutes, get in and see the temp gauge at hot (middle) and no hot air comes out until i get the car moving fast enough.

any ideas? help. it;s going to be a long cold winter this way

 

Im having a similar issue i have yet to fix since im kinda busy but you can do a diagnostic check on the ac system. To do this turn the car off press the auto switch and circulation switch at the same time and turn the key to the on position. It will give you a number/numbers. If you can find a factory service manual for the sc400. It will have an a/c section which will tell you what the problem is. If you cannot find what a manual let me know what codes you get.

For the warm air in the mornings, it is because the car/coolant has not warmed up yet.

 

Hello. I have the same problem. Can somebody give me a solution what is wrong?

 

Have you all checked the vacuum lines going to and from to see if they are ok? Also check the inline one way valve, if I am not mistaking. Try to bypass this and use a straight piece of vacuum line and see if you get other than hot.

 

Somebody that was a Master tech in Lexus said that it's the Climate control computer. I'd do a little more testing before replacing that part...

 

Thanks guys. I did the valve control bypass and its better, but its still not it.
I am going to put more coolant i already bought but the thing is i DONT KNOW WHERE TO PUT IT.
I got small experience with coolant etc so please help me, would be nice if someone put a picture here where to put the coolant water. I need to fill up because i am sure its arround 1l missing, so it can be the cause.