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had the a/c fixed(replaced) glad I bit the bullet on that because even in Southern California it can get hot. There is a problem, I can't get the air mix servo to return the arm it's attached to back to max cold after turning it up to max hot. It gets stuck halfway on the way back down. The servo is new and works fine. I attached some pics for reference
Max cold
Max hot
This is where it stops from max hot back to max cold. I can push it back to max cold with my finger.
Is the air mix servo tightly affixed to the mounts? When you manually move the blend door arm (with servo removed), does it feel like there is excessive resistance? Also try lubricating the track on the blend door arm. If those items are ok and it still doesn't work, you may have a weakened motor in the servo. My mode servo motor became weak and would not go to the top vent setting. They do wear down over time.
All three servos use the same motor, so you can swap them out if you dont mind removing the servos and taking them apart. The air recirculation servo can be used as a motor donor as described in post #27 here: https://www.clublexus.com/forums/rx-...made-easy.html
There is a lot of other good info on servos in that thread as well.
Unfortuntely, I am not aware of a replacement motor that can be purchased for these servos.
The pictures say "spring loaded bell crank". Looks like the spring is on the black crank.
I can't tell from your pictures, is the spring hooked in place on the top of that crank?
Also, why not go back to the guys that replaced the a/c and tell them they messed up somewhere?
Screws were double checked, I thought about that one too. And all the appropriate springs are in place. There is quite a bit of resistance, but with a firm push with my finger it will go all the way back down. Greasing it up didn't help. Still gets hung up. That servo is only about a year old, I guess it's possible it could be defective. I could replaced it again. Now that I know how to do it, it's a breeze.
If you have a new servo and you feel resistance at the door, it sounds like the blend door is the issue. I do not know of any threads on accessing the blend door. You could try manually rotating it with the servo removed, and use some compressed air to blow into the plastic bearing to clear out any material that has accumulated in there. Also run the fan at max while you are rotating the blend door to help loosen any impediments.
Looking at picture #2 [max hot], I see scratch marks which is sign of something scraping. The scarping can result in drag. I would re-examine the servo to housing clearances.
It seems you are missing a screw that holds the servo to the housing and it could be that when you operate the servo, it is getting racked and the plane of motion is getting disturbed. There is a always (mostly) a reason why the manufacturer puts in a screw.
After digging around again (that missing screw Salim is where the duct for the floor mode get screwed into, I have to take it off to get to the air mix servo, which is the area with the problem).
The servo is 100% ok. It's an issue inside the white box everything fastens too. The door gets stuck right between the hot and cold mixing. There doesnt seem to be a way to service that unless you tear the entire dash apart. And replacement for that white box is over 2 grand.
So looking for other ideas to unstick that door externally.
It sounds like you feel the servo motor is fine but the door is binding at a certain point. You are able to push it past the bind point with your finger.
What is the servo motor doing when the door gets stuck? Is the motor in it stuck, trying to push the arm but cant?
Then when you nudge with your finger the arm travel resumes under motor power?
Not seeing what is happening makes it difficult to know what to do. You can get one of those cheap borescopes from Amazon that connect to your phone and thread it through the vents into the blend chamber to try and see what is catching the door when it moves, or if there is something broken with the mechanism. If that doesn't work because of difficulty in feeding it into the chamber, you may also have to drill a small hole in the side and feed it through there.
The reason I asked was I was wondering if the worm gear in the servo was slipping under the high torque condition. From the video it's hard to tell.
When the servo arm hits the bind point (which also has the least leverage on the cam) it tries to climb out a bit, and then just seems to quit. I kind of expected to hear some clicking and grinding from the motor. I once tried to hold back a servo arm and it was much stronger than I was expected.
10-14-16, 05:30 PM
A/C fixed but still a problem
