2007 Lexus Ls460

Problem started after car battery was dead for several weeks during Covid.

Symptom: On starting car, there is a repeated plastic-against-plastic sound (one click every 2-4 seconds, regular) from passenger side left foot area of the dash.
The clicking goes on for a few tens of seconds. During this time, the A/C button is lit, but the A/C is not on and other the A/C buttons (recirculate, etc) are also not functional. When the clikcing stops, all A/C button are off. Now, I can press the A/C button and turn it on, have to set the temperature each time, and can use the other buttons as well. A/C works.

Over time, the period for which the clicking sound lasts grew longer and longer.

As of last week, the clicking sound goes on for minutes and at the end, I can't turn on the A/C.

From my google searches, I have come to understand that this is a rare but known problem. It seems that the sound is from two servo motor arms colliding with each other and that these are part of the recirculate vent mechanism. Apparently, the servo motor is not properly initialized -- the motor is in one position, while the computer thinks its in a different position. So, the computer tries to move it to some position, but fails to do so. Until the computer gets the correct signal from the servo, it wont let user operate the A/C. Something like that.

Does anymore know more about this problem and its solution ? Is there a way to properly initialize the servo ? If I am happy with the A/C being permanently in the "recirculate" mode, is there a way to work around this problem ? Will resetting the ECU do it ?

related youtube video:
thanks,
mmsharma

 

Message me I will send you the LS repair manual

 

If Sherl is sending you the manual, check out the "check mode" detailed in the A/C system section. If you press and hold "AUTO" and the circulation mode buttons while turning the car on, the HVAC system will go into a self-diagnostic mode. Even if you don't have Techstream set up, you can use this to iterate through the servos in the ducts to try and isolate where the problem lies.

The servo's don't just randomly get mis-calibrated though; the only way this could happen would be a physical blockage in the duct, or the gears wearing or breaking. I'd be surprised if running the initialization function alone resolved the problem. Even in the video you linked, the guy mentions that the most common servo failure, the circulation control, is caused by people forcing the door open for filter replacement. If it's physically broken, no amount of initialization is going to fix it.

Strange that the system is completely shutting off though. If you want to run the initialization then you need Techstream, and if you have that you can check the specific codes being reported by the A/C amplifier to see what it thinks is happening.

 

Exactly. Mine has it broken because people didn't know how to change cabin filter and ended up with replacing servo that actuated the door

 

Folks, all I needed was a "AC SERVOMOTOR INITIALIZATION". My friendly mechanic put it on his OBD scanner, but found no codes at all. I nudged him to explore a bit more and we came across the above function. Pressed the button, restarted the car, and everything works normally.

Thanks for your help.

 

This problem and solution is also mentioned in the following thread: https://www.clublexus.com/forums/ls-...em-solved.html

 

I've seen quite a few threads where a damaged gear was found to be the issue. Glad your's wasn't.