JonSnow

In my case the one I pointed to is the one that was bad. Of course I hear its common for both to go bad. Still haven't got around to replacing it yet. What did you pay for the replacement?

DrDan

I can't quite get a grip on why there is a ticking sound behind the glove box when my A/C vents work correctly. The sound appears to be a searching activity, but it does not result in any mechanical changes to the vents. I am trying to justify taking the servo out and cleaning it, like described elsewhere, but I am also a believer in, "if it ain't broke, don't fix it." Any words of wisdom on this one?

salimshah

That is what the servo is trying to do,

You need to zero in as to which servo, Typically it is the mode ... connected to the mode **** through the ecu.

Salim

mindfull

READ THIS BEFORE YOU BUY NEW SERVOS!
https://www.clublexus.com/forums/6965677-post214.html

takaiguchi

That fixed it for me! I tried so many different things with all the writeups and this is what finally fixed it. Instead of gluing it, I took a small piece of paper towel and put it on the metal rod and then inserted it into the plastic gear cover. It kept it tight and now it works like a charm! I forgot what it felt like to have cold air on your face!

Thanks!

RoX300

I've been living with the dreaded annoying hamster clicking noise one of the servo motors is generating. What's the fastest way to diagnose whether it's the Air Inlet Servomotor, Air Outlet Servomotor, or Air Mix Servomotor? From what I'm gathering from this thread is that most typically it's the Air Outlet Servomotor (is this the one some refer to as the "Mode" Servomotor)?

I've attached the RX300 Air Conditioning repair manual which includes good diagrams and instructions for removal of each of the servo motors.

salimshah

Elementary Dr Watson ...
Mode servo is either driven by AUTO or mode ****/button. Switch out of AUTO and see the servo respond to your settings and then stay put (or try and try and quit).
Mix servo responds to temp setting (hot or cold) while the compressor responds to temp settings + A/C switch.

Salim

RoX300

Thanks again Salim. I will give that a try.

chococat

Wanted to thank everyone for every bit of information posted here about the servos. I just brought my "new" 01 RX home yesterday, bought it knowing it had servo issues.

Took apart one, and it was indeed the wormgear. Re-positioned it, cleaned everything, put it back in, and all "modes" work. Switched from vent to vent flawlessly.

The laughable one was the one that switches hot to cold. It doesn't work because the white arm was completely broken off and missing. Guess that will have to mean a new part. Part # on that one was 0637000-7061.

I had three pictures, but they are viewing HUGE...so I just left them off.

japatric

My first time posting here, thanks for all the DIY help on air mix servo. Mine failed about a year ago, so I changed it out using the help here. Now the servo switches through the damper positions properly (hot to cold) but the servo motor itself seems to want to keep on driving past the full code position - it makes a horrible grinding noise (intolerable to drive with it). When it makes the noise, I can gradually back the temperature higher and the noise will stop for a short time, but as the cabin temperature rises the noise will begin again as if the servo is trying to command the damper back to full cold position (even though it's already in full cold damper position). It's seems as if the motor can't sense what position it has put the damper in and wants to continue to drive to full cold. I'm thinking of assuming the servo is bad (maybe I just got a faulty one) and switching with a new one, but then afraid that maybe it's something in the ECU servo instead? I hate to spend another $150 on a new servo only for that not to work. Any ideas? I couldn't quite find this failure described in all the air mix servo threads posted. Thanks

salimshah

I am assuming you did not open the servo and the servo arm is still in the position you received it.

Remove the servo and manually move the lever that the servo drives from one max to the other max. Make sure all the mechanism moves freely ... there could be a combination of parts that are driven directly or indirectly by the servo arm. Then reattach the servo and force the lever to match with servo position.

2nd option:
Remove the servo and reattach the wire connector. Using temp control (if we are talking about the mix servo) and make it cycle to max movement (there should not be any grinding noise). Leave it in max or min position. Move the lever manually to its extreme position and see if the arm of the servo matches [if not push the lever to the other extreme .. one of the two extremes would match]. Fasten the solenoid.

Note: Under no circumstance should you move the arm of the solenoid manually. Only move the levers that the arm would move when the solenoid is in place.

Salim

japatric

I appreciate your suggestions salimshah. Here's what happened. I did your option 1 (disengage servo arm from damper arm), and the damper moves freely between extremes...... hot air blows out when I push the damper to the extreme "up" position, and non-hot air blows out when in the extreme "down" position (unfortunatley my A/C has a leak diagnosed as a leaking heat exhanger with a $1800 repair job, so nothing cold comes out now).

I didn't actually go through your option 2 as I'm avoiding taking the pesky servo completely out unless I know pretty well that the servo is bad. But, while I had the servo arm disconnected from the damper arm, I dialed between full hot to full cold a few times on the A/C temp control dial. The servo moves the servo arm full in one direction (what I would imagine would be full hot if the damper arm was connectoed) and stops (when dialing to full hot). When I dial to full cold the servo moves the servo arm in the opposite direction and then when it hits what I envision would be the max damper full cold position (if it was connected) the servo arm stops moving but the servo gears make the horrible grinding noise as if they are still trying to drive the servo arm further.

I'm concluding then that it's an electrical issue in either the servo or the ECU. One, either the servo is not sending the correct resistance output (black wire coming out of the servo) to the A/C ECU so that the ECU knows to stop sending a motor current. Or, two, the A/C ECU is receiving the proper resistance level from the servo, but the ECU is not shutting off the current for whatever reason (maybe it's out of resistance calibration on the hot side only).

I'm leaning more towards it being the first problem (servo sending the wrong resistance level), but I'm not sure how to verify whether it's the servo or ECU unless I take the servo out, open it up, and give it a good dielectric treatment to get the resistance feedback circuit to work again. I've tried to attach the electrical diagram from the manual.

When I reattach the servo arm to the damper, it again moves the damper arm properly to full hot (when I command to full hot), and when I command to full cold it moves the damper fine to that position, but then starts it's grinding noise when reaching full cold. Then if I back the temperature dial just a little bit warmer (say 74 degrees instead of full cold), the servo arm motor won't move the damper arm from full cold, but the grinding noise will stop (i.e. the servo motor stops trying to drive the servo arm).

salimshah

The litmus test was to run the servo without anything connected, and in your case that was a problem.

That leads to two possibilities:
1. The servo is bad.
2. The wires or the ecu that gets the position information from the the servo and controls the voltage to the motor is bad.

See if you can get hold of the manual that states the expected voltage based on position of the servo arm.

Keep in mind the horrible sound you hear is the nylon gear getting rounded off as one piece moves and the other does not.

If you had the option of throwing parts at it, you could try another servo (or even old servo for grins), another ecu.

You should ask yourself that is it worth fixing without the other $1800 fix.

Salim

japatric

Thanks salimshah. Yep, it's coming down to taking a crap shot and trying either another servo or ECU - good point about the gear grinding though. I did realize this is what was happening, but maybe considering I've already damaged those gears quite a bit with all my troubleshooting, I may just want to start there and get a fresh one hoping it fixes this particular problem and having fresh gears now that this servo has an unknown amount of wear already.

Or another thought I had was to install a cutoff switch to this servo..... let the servo command to full cold then flip the switch to cut power off to the servo manually (then reengage power whenever I want it to get warmer). I did a similar jury rig for my drivers side power window when it would only go up and not down (instead of spending $200+ on a new circuit board/drivers side window control unit).

I agree completely about whether I should continue throwing money at this thing given the $1800 A/C fix, along with the driver's side window controller I need to replace, this servo problem, and the annoying P1130 code I've got (that seems to make a guess reappearance despite how many times that Ox sensor is replaced). I don't need a perfect car, but no A/C in Texas summer is not very comfy. And, considering I can't get much for this car on trade in with it's existing issues and I'd pay almost $2K in just sales tax on a new car, maybe the $2K to fix is worth it if I can get another 5 years out of it.... as well as let my child learning how to drive in it (I certainly wouldn't be too upset if she wrecked this car).

davidyal

Last Dec, I was only experiencing cold air. So, I removed the MIX servo, cleaned it, and voila the heat came back.

Now, come this summer, it just feels like my AC is not that great. My Freon levels are good, the mix servo appears to be fully in the Cold position.

Any idea what could be causing my air not to be as cold as it should be?

One clue is that when recirc is off, the air seems a bit colder. Could another servo be in play here? What's the best way to isolate. Pressing the Mode button seems to cycle properly thru the vent positions.