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Headlight leveling sensor failure - detailed post with pictures

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by FirstFlight, Jul 1, 2012.

  1. FirstFlight

    FirstFlight Member

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    Last month my red triangle would pop up along with the yellow head light symbol. Most times it would be for a few seconds, other times it would stay on for a few minutes. Today I rotated my tires and I thought I would check out leveling sensor while the tires were off.

    I took my left rear tire off and this is what I saw when the sensor was removed. Sensor view with tire removed.JPG

    So everything looked normal to me. Looks can be deceiving. I've seen pictures on here of leveling sensors where the guts are completely rotted out. That's what I was thinking I was going to see. Here is a picture of the bolt side of the sensor:
    Sensor before disassembly.JPG

    Again, it looked normal to me. If you don't know what you're looking for, especially if parts aren't mangled, it can look normal. So I took the four screws off of the sensor and this is what I saw:
    Sensor - Both sides.JPG

    Sensor - spring side.JPG

    The inside of the sensor was in pristine condition! The springs are shiny gold and there was only a small amount of dust inside the sensor. I started to think about how the sensor works and I figured out that the sensor must move in some way. Hmmm. But there was no bracket on it to turn the sensor. Hmmmm. But it's a potentiometer, it must move!

    I tried to turn the shaft and it would not move. I looked more in detail at the bolt side of the sensor and realized that there was part of a broken bracket on the bolt. I went back to the area where the sensor is mounted to take a closer look. Ah-ha! Now I understand what happened. Here you can see the broken leveling bracket:
    Sensor view with leveling bracket.JPG

    Ok, so at this point I figured out that the shaft seized somehow and it broke the leveling bracket. This led to a more detailed investigation of the sensor and why I'm unable to turn the shaft. With the bolt and broken bracket removed (and some cleaning), I was able to see what happened. Sensor with failed seal.JPG

    The seal failed! I took it out and it's clear that after the seal failed it let water penetrate into the shaft, which caused a lot of rust. Here is a picture with the seal removed:
    Sensor with bearing removed.JPG

    You can see there is a lot of crap there. That also means there's hidden rust in places that we can't see. I removed all of the visible rust and here is a picture of the debris (with the shiny like-new spring):
    Debris from bearing.JPG

    Here is a picture of the busted seal and part of the leveling bracket.

    Broken parts.JPG

    I also took a picture of the seal part number:

    Bearing part number.JPG

    And finally, what's left of the leveling bracket:
    Broken leveling bracket.JPG

    So here's where I'm at now. This sensor is pretty damn expensive! Used sensors on E-bay at listed for more than $250. I'm not much of a mechanic due to a career in electronics. I sprayed white lithium grease into the sensor a bunch of times. I would work the sensor back and forth, use Q-tips to remove the lithium grease and debris and then repeat. It's definitely easier to move than before but having previously worked on a leveling system for transportation vehicles, it still seems there is too much friction.

    A new or used sensor isn't an option right now so here are my questions:

    1. Would something like WD-40 be a better option to try and revive the shaft back to like-new condition? Is there something better I can use?

    2. An internet search for BE3177F (the seal part number) reveals nothing. Providing I can get the shaft to move freely again, not having a good seal in there will only create more problems in the future. Does anyone have another option I can use for a seal?

    For now I just pointed the lights lower so they don't blind other drivers.
     
    SFO, Patrick Wong and cwerdna like this.
  2. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Nice fault analysis.

    Perhaps Steve at autobeyours.com can help with a used part?
     
  3. johnjamis

    johnjamis Junior Member

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  4. johnjamis

    johnjamis Junior Member

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    It looks like the 3 wiper tangs have a coating on them. Mine were clean and shiny. Try cleaning the tangs very carefully as they are fragile.

    My sensor arm was also very tight. I used wd40 and penetrating oil for quite a while and it eventually freed up just a little and has been working fine. It is still somewhat stiff.

    For the broken arm. This is a simple fix with a welder. Maybe $10 at your local welding shop.
     
  5. jadziasman

    jadziasman Prius owner emeritus

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    A very poorly designed sensor. The only issue I've had with my Prius to date.
    And now yet another way for it to fail.

    What a PITA! Oh what a feeling.....Toyota.
     
  6. SteveLee

    SteveLee Active Member

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    What was the outcome of this failure repair?
     
  7. ChristopherH

    ChristopherH New Member

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    I have a related question....
    If one has switched to halogen bulbs and halogen assemblies (like I have) ..
    and those assemblies do not use any type of auto - leveling system (the ones I have ...have manual adjusters).
    How can I get the car to STOP displaying the warning light about the auto - leveler sensors ??
     
  8. jadziasman

    jadziasman Prius owner emeritus

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    Your Prius is equipped with a headlight beam level control ECU.

    It seems that if you disconnect the wire between the headlight beam level control ECU and the combination meter then all of the warning lights might disappear too. It is the H12 connector on the ECU and it's the WNG wire.

    Unfortunately, it might not be easy to get access to the ECU. It looks like it's bolted to the firewall behind the glove box.