I have a 06 SC430 with 52K miles. I have had the vehicle from new, maintained it well and have had no other problems over this period of time. In short a fabulous car and intend to keep it!

The one issue though that I need to correct and should have followed up sooner is the fact that when the top is down it always blows warm air from the lower and lap vents which is great during the fall months in the northeast but somewhat uncomfortable during the hot summer.

I would assume it is a sensor or computer problem but am wondering whether anybody else had similiar experiences before I take it into the dealer?

 

Do you have it in the auto setting?

 

When I have the top down I don't have the auto settting engaged. Good point but following through if it's not engaged why is it then pumping out warm air?

 

Is the a/c button pressed? If not, that could be the reason because it compresses the warm air and helps to get rid of the humidity in the air.

 

Set the temp as low as possible with the heater on. Then switch the heater off completely and there is no hot air coming out of the vents anymore.
I think all the valves are electronically controlled and they keep there position if the heater switched off so if the valves are on low temp no hot water is flowing through the hoses. And if they where on the hot position well.... The same where the air comes out, top or bottom.
Maybe only the heater fan is switched off and all the other setting are staying the same

Works on my 2002 SC.

All the best

Willem

 

I have the same issue and I have tried different settings and nothing stops the warm air coming out from below the dash. The fresh air/recirculating air control does nothing. The temp setting has no effect, and the only way is to turn the AC on with the top down! It kind of felt like the warm air is from the engine's own heat and somehow came through the firewall and drown out from under the dash, because the upper vents still have fresh air(col air) come out. It makes no different wether I shut off the vents or not.
By the way, mine is 2002 with 110k miles on it.

 

No the a/c button is not pressed and the climate contol is completely off. As BB430 mentions it almosts seems that it is radiant heat getting through the firrewall. I have also played with various climate contol settings as well and I have had no luck with solving the problem.

This vehicle is so well thought out and designed that I don't believe it is a systemic problem for this line and I am sure it's an issue only for the few of us.

Funny thing about this car it's the only vehicle I have ever owned for an extended period of time where I still enjoy driving it almost as much as when I first drove it.

 

Actually this is a design "feature", though not a popular one... The only thing to reduce the effect is as mentioned above to set the temperature setting very low before turning off the a/c or else leave the a/c on to a comfortable temperature.

The other option is in the C-Best settings. (Do a search and you'll find earlier threads a few years ago on it. There are also lists in earlier threads showing what all is controlled by the C-best settings.) You can take it to the dealer and have the C-Best setting turned off that blows hot air on the feet when the top is down.

Good luck.

 

I also have an 06 and this is the exact behavior I experience with the climate unit off UNLESS I press the fresh air / recirculated air button. As long as the button is set on recirculated air, there is no blowing.

 

I've been fighting this demon since I got my car 6 years ago.

Here's a thread...started by JohnnyCake,back in 2007...talking about it.

What I've found (I posted it then and I still stick by it) is that it doesn't always do this.

From a cold start, it dosn't do this. Everything works fine; "OFF" means off on the climate control system.

It's when you shut the car off, and do a "warm start" (starting the car when it's already up to operating temp). That...combined with the top down...is when the hot-foot happens (at least in my car).

I've just gotten into the habit of setting the climte control on "foot", setting the temp at about 75 (ambient-ish temperature) and turning the fan on about 3. That seems to be a good balance. It doesn't feel like there's cold air blowing on your feet/legs, but it's enough to override the hot blowing air.

 

On the SC400 / LS400 there is a heater Vacuum Solenoid Valve (VSV) which gets stuck in either the fully open or close position. The VSV controls the amount of heat and cold coolant that goes into the internal cabin radiator.

I'm not sure if the SC430 has this but I would assume that it would have a similar setup.

Check that the heater VSV is working.

https://www.clublexus.com/forums/per...rol-valve.html

 

Thank you for all you guys help and links. At least I know I'm not crazy and I have an issue that some of you guys are experiencing as well.
I'll try to excersize some of your great advices and see what improvement I can find. Any great solution I found, I'll pass along the way.