Evenin' all:

The mode servo in my 1999 RX300 has been going out for a couple of years now (continuous light clicking noise symptomatic of the problem). I was going to just live with it as the servo worked (it changed the air deliver modes as requested) albeit noisy. Now there is the awful loud buzzing from under the dash that starts and stops randomly and the mode switch has stopped working altogether (the indicator on the dash says the airflow direction is changing but the airflow itself only comes out of the dash vents).

Is this just a last gasp symptom of the mode servo going out (has anyone else experienced this) or is there something else crapping out in there?

Thanks,

 

did you already adjust the yoke on the servo worm gear? If not, check out #71 of this thread https://www.clublexus.com/forums/rx-...x-servo-2.html

 

No, I'm not planning on messing with the old servo - I'll just replace it. Just wondered if anyone had heard this loud buzzing rather than the more common "hamster wheel" ticking?

 

hamster on a wheel sound is constant turning of the servo.

Buzzing sound is when the motor can not overcome the detent spring. You can open the panel up and see the poor thing trying to push and fail. Give it a nudge and it flip over and the buzzing sound will go away.

But you recently replaced the servo. That leads to a possibility that the arm has reached the extreme position but the servo wants to turn more as it and the controller think there is more to go. Try disconnecting the servo and move the arm of the cut to one extreme. Do not attach the servo to the arm and put the connector on. Switch modes and observe the servo move. Your task will be to position the servo that you have the servo arm in the same extreme position. Once the positions match, attach the servo.

Salim

 

Hi Salim: No, I didn't replace the servo - I've been putting it off! When you say the motor cannot overcome the detent spring, what exactly do you mean? Is the detent spring in the servo or in the air box?

 

consider adjusting the yoke on your servo. It's less than a 5 min job. If it doesn't work, no loss. New servos are $100+. It takes more time to remove the glove box than replace the servo if the glove box hasn't been removed before. Those screws can be lodged in there tight.

 

What do you mean by the yoke? Is that the arm coming out of the servo unit? How does it come out of adjustment?

 

My bad, I thought you had replaced it. So ignore most of my post.

Detents: If you recall slider based controls, they have a designed feature to slide and stop. each of those stops are detents. Take the panel off and see the servo make effort and give it a nudge.

Salim

 

Please refer to the 3rd video in post #71 , in the link I referred earlier. It explains what typically goes out of tolerance. At approximately 4 minutes, the video shows how to adjust.

 

OK, fastnoypi, that noise is exactly my problem and the mode function has gone AWOL, so I'm guessing it is the mode servo and that the internal worm gear has come out of alignment.

Thanks! (and thanks Salim - I'll check that while I'm at it)

 

I dug around my cellphone. Here is a pic for future reference. I used a flat blade screwdriver and just twisted it underneath the metal "yoke" to move it a few mm up the motor shaft to make the worm gear snug.

 

If you disconnect the arm and pop the case open, please mark the position of the arm and the large gear and they need to go back in the same relative position. The wiper contacts tell the ecu where the arm is (which vent position you are on). Worm gear on the motor can be in any position, jut needs to be mechanically bound to the shaft.

Salim

 

I think I may be having the same issue. For the first time since I got my rx a little over a year ago I turned the car on and I started getting like a loud grinding noise coming from what seems like behind the glove box which leads me to believe it's either the mode servo or the air mix servo only I'm not sure which one. Is there a general way to tell which one it is or do I have to yank the glove box out to find out

 

Move the temperature to hot, until it gets hot and then to cold, until it gets cold. If the temperature changes, the air mix servo is probably OK. Then move the mode to windshield, face and feet. If the airflow moves where it should, then the mode servo is probably good. I'm guessing one of them won't be working (if its the same loud buzzing that I'm hearing and in the first video, above).

 

Mine started the buzzing noise 6months ago, now its ridiculously loud, believe im gonna watch the video and try to adjust it, thanks!!!