Retroplay

Many users here have complained about the heater blowing hot air on their feet while the hard top is down.

While poking around in the repair manuals, I have stumbled on some information which could possibly resolve this.

First, it is listed as a customizable feature. Techstream should be able to turn this feature off.

The applicable feature is listed as:

Name: FOOT AOUT OPER (Foot Air Out Operation)
Default: ON
Description: Function to turn air flow from lap−jet ON automatically when
retractable hard top is housed
Settings: OFF/ON

I think some have mentioned that they had this set at the dealership but it was still blowing hot air on their feet. Looking in the wiring diagrams, I think I can see a way to absolutely disable it, but need to study it a bit more (why I named the thread teaser)

The lap-jet servo is an entirely separate motor specific to this purpose. There is also a return from the hardtop ECU to tell the A/C control when the top is down. You really wouldn't want to disable this input because it is used for several reasons including the status of the open/close switch itself. But, you may be able to disable the output to the lapjet servo.

I am going to look over everything and see if I can find a reasonable solution that won't cause any error codes if others are interested.

I would just like to confirm my memory stated above. Have users here already had this customization done at the dealer and it still blows hot air? If that does solve the issue, it would be a waste of time to look for another solution.

ShawnOk

iTrader: (1)

So I altered by C-Best setting in the method you mentioned above and had them turn the FOOT AOUT feature off and it really did improve the hot air on the feet with the top down... Seems like you're going to take it one step further tho. I highly recommend everyone try turning off this feature via the C-Best setting before taking on a more complicated procedure. It really made a world of difference with minimal altering by only doing the C-Best settings.....

here's the link...https://www.clublexus.com/forums/sc4...-function.html

Ps. it also help to turn the temp down to about 65, then turn the entire blower system OFF. That way that last temperature before turning off will stay and any minimal air that does blow on the feet will be that temperature. Very odd, but works for me.... without an more invasive mod.

Retroplay

Agree 100%. If that solution is satisfactory, then just leave it at that. The mod I will be outlining will require splicing a switch into one of the wires, at least.

The lap-jet sounds like the intention is to retain air pressure so driving with top down doesn't create a vacuum.

Shawn, do you know if that setting is found in the Techstream software? I am not near my computer with the software to check it.

There is also a feature to turn off the foot/defroster when in auto mode. I wonder if you need both of these off. The lap-jet probably goes into auto mode.

Hmm... maybe I should wait until spring when I can drive with the top down to test it myself before giving out any information.

Bgw70

I turned mine off as well and the warm air on my feet stopped when I dropped the top.

Retroplay

So this confirms that it is not an issue once you change that customization? I have not experienced it myself, but a user had asked me to look into it before. I noticed some people saying that even after doing the customization, it still blew hot air on them.

I will hold off on exploring this further.

Bgw70

The first time I turned it off, I still felt warm air when I opened the roof, several weeks later, I cycled the feature on then off again, this time it accepted the tech stream input. Or the servo was not functioning correctly.

I actually found a couple of fault codes relating to the HVAC system. I reset them but have not checked the tech stream again to see if they came back.

The more I use tech stream the more I realize how valuable this tool is to me.

ShawnOk

iTrader: (1)

I believe the option can be changed with TechStream, although I'm not sure how it is done. I had an official Lexus dealer change the settings for me. The pressure theory makes sense. Anyway, I think the option to change the C-Best is much easier and then see if the driver accepts the remedy. Adding switches and such could cause a few more unpredictable issues. I know Retro is a genius when it comes to these types of troubleshooting, so if anyone can figure it out, it's him. One thing that I will mention here that would be great for Retro to figure out, is why the ML amp changes phase on the rear speakers when the top is up vs. top is down (and how to stop this change). Just something more to add the "strange quirks" list.

GmanSC

Just a dumb question: how does the Tech Steam work. Do you connect it to the computer?
The other issue the ML amp changes the phase or volume, I think for wind noise compensation. Why do you want to turn it off?

ShawnOk

iTrader: (1)

Don't want to hijack this thread, but as for the phase of the speakers in top up vs top down, it's a little annoying. With the top up it's a little more of a "concert" mode with the rear speakers out of phase compared to the front to create an "echo effect". Drop the top and then they are in phase. I'd rather they were just in phase all the time. It makes more of a difference when I listen to my media player for movies, when sound should come from the left (like a helicopter approaching from the left) it's always left front speaker and right rear speaker. Confusing to the brain. Additionally, It also happens with music.

Cube

I never knew it was the heater blowing hot air. I always thought it was just hot air resonating from the engine.

My temporary solution was switching on the A/C to cool the knee down.

Retroplay

Yes. You plug it in to the OBD port and then USB on a computer. The included software allows you to read and customize certain features of the car, such as headlight auto-off delay, the way the doors lock/unlock, etc...

It can also display sensor readings in realtime, allows you to run diagnostics tests, and read/clear trouble codes.

Well worth the investment.

Retroplay

Hmm, interesting. I would probably need to experience it myself to really understand it but it sounds like you are saying there is a delay in the rear speakers when top is up, but no delay with the top down?

If so, that would have to be handled in the amp. Looking quickly at the terminal pinout for the amp and radio, I don't see any signals relating to the hardtop, only a sensor for the speed (adaptive volume control). It would probably have to use the AVC-LAN to communicate that.

Is it possible that it is just a perceived difference because of the change in environment?

Bgw70

turn the radio on the next time you lower the roof, when the sequence is finished the sound will be louder and it does sound differently from before when the roof was up...I did not know it did a phase shift and will try to listen for it.

GmanSC

I really think when the top's down, the computer raises the volume up to compensate for the wind noise. Do you guys notice the right side mirror tilts down when you put the car in reverse?

Retroplay

Yes, I thought something was wrong with the first time I noticed.

My driveway is on a slope and I only really notice it when I back down that. Do the side mirrors adjust for the incline like the headlights do?