chikoo

Hi

since the last few weeks, the air on my 2001 RX300 is stuck to the front position. I put it in Auto, it shows blowing hot air ot the feet, but the hot air still comes out of the front vents. If I manually change the position, the icons change but the air still blows out the front. I also not not hear any clicking or buzzing sound indicating the gates are being opened / closed.

What could be the problem? Any ideas?

TIA

code58

Chikoo- sounds like a very good chance you are experiencing the infamous "air mix servo failure". There IS a POSSIBILITY it is something else but that is the most common failure. There has been quite a bit posted on it, on this forum and the other major Lexus forum, so you should have no problem finding it if "searching" under the above quotes.

chikoo

Code58, thank you. I did find the threads, but not sure if that applies as there is no mvt heard from the servo even after i opened up the dash....could it be a relay or fuse?

code58

I wish I could help more Chikoo, the RX is my DIL's, I'm only the volunteer mechanic on it. I remember someone posting a trick where you can put the controls into a mode where they will read out a trouble code in the "display" window. I believe it reads out a # and you have to look up the # to see what the problem is. Self diagnosis in other words. If I had the manual I could look and see if there are fuses or relays, but the manual is with the car. I've done a lot of electrical work and have the equipment to diagnose, but that's pretty much hands on work.

Here is the procedure for the self diagnosis. https://www.clublexus.com/forums/rx-...sn-t-work.html

chikoo

Can somebody tell me which is the Mode servo?

Thanks!

chikoo

Fantastic....I will try that.

MASSMINI

The lower one (hidden by duct in your pic) is the mix servo. Upper one is mode servo.

chikoo

so in my case where the air flow is stuck only in 1 position, should I be replacing only the Mode Servo or the Mix Servo?

Edit...I need to replace the Mix Servo. Got it!

TIA

bmwboyee

Could you tell me how you removed all that stuff? I need to get back to the blower control module and that looks like it would give me access.

MASSMINI

Mix servo controls the mix of hot and cold air - in other words the temperature of the air coming out.

Mode servo controls where air comes out - floor, dash, defrost - corresponds to the 'mode' **** on the dash.

Sounds like your mode servo is faulty. Removing, opening it up, and cleaning can sometimes fix it. Worked for me with the mix servo. Many posts on the topic. Search for 'air mix servo' or just 'servo'.

code58

I believe MASSMINI is correct. I have been guilty of calling it the "Air mix servo" and I believe the problem servo is actually the "Mode Servo". I have worked on it on 2 different RX's and the problem was the Mode Servo both times. It's the one that makes the "rat scratching" sound after you shut it off.

code58

Chikoo- I would suggest you pull the cover under the R side of the dash and then pull the glove box and door assy. Then operate your controls and you'll be able to SEE which one isn't working properly. You know now that the UPPER one is the MODE SERVO and the LOWER one is the AIR MIX SERVO, so you'll be able to actually watch and see which one isn't doing it's job.

chikoo

Shucks... I thought mode servo meant outside air or recirc air mode. Glad i did not swap out any. Anyways the mode servo(top) is not responsive at all when i change modes. Doesnt even try to move. I cleaned plug contacts but to no avail.

chikoo

That is super easy. Open the glove box and remove the bolts on top left and right corners. Do the same below the globe box.

MASSMINI

The contacts to clean are actually inside the servo. There's brush style contacts in there that sense the servo arm position. You have to remove the servo and open it up to get at them. Did this recently on the mix servo and it's worked fine since. Mode servo is much easier to remove than mix so you're in luck there...