Hey everyone, just wanted to start by letting you all know i used the search function and i know there are past posts about the issue my car is having. Its a 2014 Lexus GS 350 F sport. The issues started happening about a year and half ago. I've limped it along since then. Basically at times some of the vents were blowing cold air and some hot. Then it started with saying it was coming out of the "upper" vents but it was blowing on your feet, and if you tried to change it, it wouldn't work all together. I've taken it in a few times, at one point we changed the control module unit that was flagging the code and the TCM. Unfortunately that didn't fix it and I'm not at a point to replace all 9 behind the dash and pay the $3500 for parts/labor. What I'm actually curious about is what they're using to reset it every time i take it in. When i get the car back the air is coming out of the proper vents and its cold. Are they using some diagnostic tool that i could purchase and use to reset it at home every couple months when it fails? I've tried the reset of holding the hvac buttons inside the car at startup but I'd assume they're using something that they're plugging up to the car to get it to reset. Would anyone know what that tool is exactly and could a regular person like myself get that from a vendor?

-Skyler

 

@Axton1188 - They almost certainly used their standard issue Techstream diagnostic equipment as standard practice to initially diagnose what the problem may be with your HVAC. Doing so may (or may not) have reinitialized the HVAC system to some degree that got the servos to operate the damper blend doors to work normally (as designed) - but only for a while - with no guarantee they will continue working correctly for any significant of period of time.

I feel sure you received the proper and correct analysis from the Lexus technician/advisor for your car's HVAC problems.

I think you can forget the idea you seem to likely have that you might be able to permanently 'fix' your car's HVAC servo problem if only you could get your hands on whatever the Lexus dealership's service department used to diagnose your car's HVAC problem that got it working temporarily. That is not magically going to fix your car's HVAC problems permanently, or any meaningful period of time...

 

Thank you for your response. I don't disagree with you in the slightest. This is not a permanent fix by any means, its me limping (temporarily) the car along through summer until I decide on a solution of upgrading or just paying to fix said problem. Basically its coming down to me being a cheap skate at the moment.

 

@Axton1188 i believe a few members have purchased the Techstream software (off Amazon/eBay) and attempted to do the reinitilization themselves. You can also go to a Toyota dealership to see if they'll charge a lower rate or a reputable local shop that has the Toyota/Lexus Techstream subscription software capable of a reinitilization of the servos.

The Lexus dealership usually charges a couple hundred bucks to do it and it saves you the time, headache and liability of getting an unexpected result if you do it yourself. See this detailed thread for more info: https://www.clublexus.com/forums/gs-...or-advice.html

 

Ask around for a good and reputable AC shop. Sometimes you'll be able to find master ASE mechanics who are working for themselves in smaller shops. A grand is a reasonable price to shell out.

 

I dont know if I'd say you are being a cheap skate, who wants to pay $3500 to fix HVAC issues, I feel ya man. Hopefully you'll find a shop or something that can replace them for less.

 

I'm starting to believe the only way to "fix" these servos "permanently" is to acquire the knowledge it takes to constantly repair them without dealership help. Knowing how to repair, replace, reprogram these servos yourself, I think is a good start.

 

Depending how often it occurs, you could limp along by disconnecting your battery when it occurs, and wait a couple mins and reconnect. That would force a reinitialization.

Of course, every time you disconnect the battery, you have to be careful with the head unit. Push the start button once, without foot on brake, and let it sit for a minute until the head unit finishes loading and you see the map. Then you can start the car.

My suspicion is that the AC reinitializes when left parked for a day or two, as I've had an AC position issue resolved itself the next time I started the car overnight. I don't drive every day, though.

 

The video on the IS servo design explained it well. That the servo worm gears have too much play and thus allowed for tolerances that weren't orginally anticipated. The positioning of the worm gear in relation to the other internal gears leaves a lot of room for error becuase the motor and gear dont work or sync well together all the time and disconnecting the battery as you said forces a reinitailization. In my case it was the drivers left most and left center vents that were not blowing any air. The code that came up was a B1455 [10] DEF A/O Servo (D).

In regards to the worm gear, was that ever addressed by the engineers?