Originally Posted by jcorava

I have saved a boat-load of benjamins with the help of this site ... thought I would return the favor. Here is a step-by-step instructions for removing servomotor (s) from a 1st generation RX.

Originally Posted by tigerpilot

Hi Folks:
Still a little confused.
ES350. No A/C from drivers side vents. Just air. Very cold on passengers side. I took the servo apart on the drivers side and cleaned everything. Re-installed and still same problem.
Do you think I removed the wrong servo?
It's a little confusing understanding the air-mix terms.
Thanks for your help.

Originally Posted by texagreek

I just had my servomotor replaced because it was making first a ticking sound, and then a louder grinding sound. But after I picked up the car from the repair shop, the ac is not cooling properly even though it had been working fine before. Did the repairmen mess something up? They claim that now I need a new evaporator and expansion valve.

Originally Posted by odinson

thank you, thank you, thank you fingershop! Your write-up was finally the one that made sense and worked, out of all the posts on this topic…of how to fix the servo motors. Many people said to “clean the contacts” but you explained how and why, which enabled me to know what i was doing and get it done right. Big kudos from me…

thank you to sakataj for posting pictures on removing the passenger and mode servos.

Thank you to dro15 for posting pictures on removing the driver servo.

Today i removed, cleaned, and reinstalled three of my servo motors (driver, passenger, and mode) using the information you guys gave, on my ’99 gs300. And now they are working great, and the noises in my dash are gone! I wish i would have done this two years ago!

So here is my contribution back to all those of you who are still reading and trying to figure out how to go about this, as i also read a lot of misleading information about these servo motors. I will attempt to clear much of this up…

there are 4 servo motors: Driver’s side temperature control, passenger’s side temperature control, mode control, and fresh air/recirculation control.

driver servo
the driver servo is located underneath the driver’s side of the dash. The other three servos are all grouped together under the passenger side of the dash.

The driver servo is by far the easiest to access, of the four servos. It is located a foot above the gas pedal, fastened to the wall just left of the radio, at the height of where the carpet meets the trim. After simply removing the cover under the driver side dash, you can pull the carpet back and see it and touch it, including its gear arm. I was quickly able to determine that my driver servo was the culprit making the “gerbil” and “clicking” noises in my dash by simply pulling this carpet down a bit and being able to feel the gear arm moving frantically back and forth continuously. I could also distinctly hear the clicking sound when i stuck my head down there above the gas pedal and put my ear up next to the driver servo.

To get to the driver servo for removal, all you have to do is take off the cover under the driver side dash. It has two screws and two clips. The two screws and one clip you can see. The hidden clip is right in the middle at the front of the piece. You just have to give a little yank/wiggle to pop it forward. Then slide the cover back to slip it off its latch. Super easy. There is no need to take out your driver’s seat for room, or your passenger seat for that matter. And it’s not necessary to lie on your back with your feet all the way up your driver’s seat. I just put a folded towel for padding on the door sill and laid on my back across that. I’m 6’2” 240. If i can get in there, most people should be able to also.

The most difficult screw to take out and put back in was the top screw of the three, for the driver servo. It’s not too hard to reach…you just can’t see it, and you are working in a pretty tight space. Again, you better make sure you have a stubby screwdriver when doing this job. The top screw was an exercise of seeing blind by feel.

mode & passenger servos
the mode servo is accessible in front of the passenger servo. The mode servo is easy to identify because it has a wide fan-shaped white gear arm. The passenger and driver servos both have a simple straight white gear arm. The passenger servo is located deeper behind the two aluminum heater pipes. And yes these pipes are hot after the vehicle runs, so beware to let them cool down. I did not find it difficult to get the screws out and back in for the passenger servo, even with the pipes there. It was cumbersome no doubt, but really only took a few minutes. A stubby screwdriver is a must! The only other tool needed for removal during this job is a 10mm socket wrench, and some flashlights. To open and clean the servos i used a mini flat-head screwdriver, cotton *****, q-tips, and isopropyl alcohol.

In removing the passenger side lower dash, i did not need to remove the blower fan. And instead of prying off half of the white plastic shroud/air-tube vent, i took the whole piece out. Its third screw is behind the plastic console trim, fyi.

fresh air/recirc servo
i did not remove the fresh air/recirc servo, as it has been said by many that this one is not known to malfunction. Whether this is true or not, i don’t know, but it makes sense that it would not malfunction like the others. Because it only has two positions, open or closed, it doesn’t have to search its potentiometer for position. It moves all the way one way or the other, whereas the other 3 servos all move to various in-between positions wherein a dirty potentiometer could result in a loss of known position.

The fresh air/recirc servo can be seen at the same time as when removing the glove box to get to the passenger and mode servos. It is behind the cd changer and to the left of the cabin filter. After pulling out the glove box, i also took the opportunity to remove the cabin filter, shake it out, and slide it back in.

“myth busters”
the following are other people’s opinions on how to fix the servo motors that didn’t apply in my case:

Username “mindfull” said the worm gear may have too much room, or a gap, at its end which allows the worm gear to slide off its shaft and disengage from the motor. This was not the case for me. My worm gears all had no gaps at their ends. Everything fit snug and tight.

Someone said to insert a washer above the potentiometer gear to make it fit more snug against the contact arms. I looked into doing this with my servos. It did not appear to be necessary, as when the cover is snapped back on, it presses the potentiometer down an extra 3/16th of an inch. This was more than enough pressure to force all the contact arms down.

It has been said to snap the arm off of the passenger servo in order to access the potentiometer for cleaning, and then super glue it back together. I feel like i was able to clean the dark contaminated grease off of the contact arms and potentiometer using q-tips and just reaching underneath the potentiometer without having to break off the arm to get to it. I can’t say whether i did a perfect job because i can’t see the result, but i did see that i removed quite a bit of dark contaminated grease with my q-tips. I then spun the potentiometer around several times using a fresh q-tip to spread the good grease around the whole potentiometer’s surface. Fyi, you must take out the motor in order to spin the gears. I would suggest going the route of cleaning under the potentiometer first and seeing if that fixes the servo, before resorting to breaking the arm off and regluing it. Though i think a break and glue could work too, i guess.

It was said that you can disconnect the arm from the passenger servo without breaking it. I inspected this arm closely and could not see how this is possible.

Some people have speculated that the plastic gears wear out, causing the servo to fail. I did not see any wear on the plastic gears whatsoever.

Some people have speculated that the gears aren’t in good enough contact to turn each other, or get off track or out of alignment. I didn’t see this whatsoever. It may be possible for the gears to come loose when you open the servo, but once you clip it back together, everything is pretty tight in there.

Some people have speculated that the motors are failing. This was not the case for me. The motors all looked to be just fine. After cleaning the potentiometer, the servo went from malfunctioning to working like new.

Some people have said to clean the contacts where the electrical plug plugs into. No, these look perfectly new. The only place needing cleaning that i could see was where the contact arms rub against the potentiometer.


cleaning the servos
the way that i cleaned the potentiometer was as fingershop outlined. I used a cotton ball with isopropyl alcohol to clean the dirty grease off the contact arms as well as the section of the potentiometer that was scraped and dirty. The dirty section is only about 90 out of 360 degrees of the potentiometer. Next, i cleaned my index finger and used it to spread the good grease on potentiometer evenly around the whole surface. For good measure, for the rest of the servo’s gears, i also smeared some of the existing grease around these other parts within the servo where i figured it should be, like at the tops and bottoms of the gear shafts, for easy spinning, and then clipped the servo closed.

Fyi, the driver servo and mode servo both have the potentiometer facing up and are accessible for cleaning, when you open them. Only the passenger servo potentiometer is facing down and therefore hard to clean.

testing the servos
with the servos installed, and before putting the dash back together, it is easy to test that they are working. When you turn the key to the on position, the white servo arms will move a little bit to initialize. When you adjust the temperature up and down on the driver’s side, the driver servo arm will move up and down. The higher you move the temperature the higher the servo arm will move up, the lower the temperature, the more it will move down. When you adjust the passenger temperature up and down, the passenger servo arm will move up and down. When you press the mode button, the mode servo will move to different positions as you cycle through feet, face, windshield, etc. When you push the fresh air/recirc button, the fresh air/recirc servo arm will go up or down and you will see the big vent above the blower open or close.

You can tell that the servo is working correctly if it moves responsively to your commands and stops. If it is malfunctioning, it will move erratically continuously because it is lost.

Now that you are no longer lost, go fix your servos!

Originally Posted by Mekhsun

The advice given by odinson below is excellent, very detailed and very precise. Great to dismantle my RX300 with ease. However for me the problem was excatly as described by Mindfull (see link below). The servo had dug a small depression in the casing allowing it to disengage from the motor key. What I did was a bit difficult. I used an old credit card and glued in a sliver of plastic to get the worm gear engaged.
Everything works like a charm!
The only thing is for these older models the clips for the casing tend to break off so be gentle. The key in pulling all of them off togetner is simple. Use little pieces of toothpicks to create the gap in all at one time and the casing half liftes off with ease.

Have fun!