Headlight leveling sensor DIY repairs - have they held up?

Life is like a box of choc-o-lates. You never know what you're gonna get.

And it's the same for that dreadful headlight leveling sensor!

I was able to repair it on my 05 and it has been functioning without any issues for the past month.

I did not need to do any initialization procedures or any other aiming. Once the sensor was functioning again, it leveled the headlights properly.

Taking the sensor off is easy. Make sure the car is off with the smart key system disabled and you can take the connector off without disconnecting the 12V battery, which they seem to want you to for every repair except changing wiper blades. Remove four fasteners and it's off the car.

The sensor repair can be easy, difficult, or impossible.

Sometimes the guts inside the sensor housing are completely FUBAR, which forces you to find a used one or shell out $$$$$$$$$$ for a $$ part.

In addition to failure within the sensor itself, one of the three blades in the sensor connector snapped off when I removed the harness and the blade got stuck in the harness side. I was not able to extract it so I had to make a work around so that the connector would still function.

My latest brillant idea was to completely surround the sensor with duct tape to prevent water/dirt/salt getting into the sensor itself and to surround most of the connector as well. I hope this will work. I purchased the thickest duct tape I could find and created a nice enclosure. So far so good.

 

I repaired mine and it lasted for about a year before failing again.

 

Question guys, Do the headlights go up and down for few sec when you first turn on the engine and the lights?
In my case, I just drove my wife 2007 prius and noticed passenger side headlight is beaming way up than the driver side one. I thought I screwed up the alignment when installing two new HID bulbs a few months ago so I took them out and found no problem. Now, after much research, I learned there is a leveling sensor in the back next to the left wheel. However, the car gives no warning light on the dash at all. When I jumped on the rear bumper, I didn't see the headlights moving up and down at all. So, the leveling sensor is bad? Or the ECU? Or the leveling motor(s)?

 

No, the headlight aim will not routinely change as you turn on the lights.

If one headlight is high (or low) compared to "normal", then it sounds like the problem is with the motor for that headlight.

If the aim of both headlights are incorrect, then I would suggest the sensor as the most likely failed component.

Could it be that your system has two problems?

 

Good idea, Eric. Please indicate the resistance spec for your variable resistor in case anyone else wants to follow suit.

 

I see. I have a lexus LS and when I turn on the lights, it goes up and down for a few sec (just to tell me leveling is working) Ok. Prius doesn't do that.
So far, I have never caught the headlights moving up or down at all but now the passenger side light is a tiny bit higher (after I reinstalled the bulb maybe), normal? Or they are supposed to be dead level?
I guess I can go under the car and see if I can move the lever to make sure it is not stuck and to see if the lights will move (giving it a few sec to response.)
If still no problem found, I will just manually adjust the passenger side light to level it with the driver side. It is possible to do a minor physical adjustment on the motor itself, right? (My wife got into a minor front bumper accident crushing the foam piece inside and I replaced it.)

Yes, it could be multiple problems. First, because of the minor accident, the headlight aiming simply needed an adjustment. Second, the leveling sensor might be just stuck/rusted but not giving error to the ECU.

Hmmm, those level motors are moving some aiming or focus reflective device in front of the bulb but not moving the bulb. Interesting...

 

I just went under the car. The lever is tied to the frame and not moving unless the suspension has load. So, I can't tell if it is bad unless I remove it for inspection. Jesus Chris. This prius has not been a fun car.

 

Great idea, Eric. Since you have already built a working headlight level adjuster, I want to know exactly what components (Radio Shack part numbers) you used and how you hooked them up. Pictures would be helpful. Thanks for your efforts.

I have also thought that a single resistor could be wired into the system in place of the leveling sensor to set the headlight level at a proper fixed position. What resistance would be correct and what would the circuit look like? John

 

please indicate the value of the poy\t or the rs part number a pdf of your wiring or pic would be nice too
great idea dude

 

Great idea. Thanks for the details on how to to make a manual adjuster for the headlights. I am going to try this the next time my leveling sensor fails. John

 

For those more daring, here is a way to have that potentiometer in the front of the car, say the glove box.

Wire the potentiometer to the headlight beam level ECU, which is under the dash on the far passenger side. Cut wires 20 (yellow), 5 (blue), and 2 (purple) of connector H12, which is the 24 pin plug that goes to the ECU. Pins 20 and 2 go to the outer tabs of the pot, pin 5 goes to the wiper. Splice enough wire to the pot to place it where you like. I have not done this yet, it's just what the schematic indicates.

You can just T-splice the above mentioned wires without cutting them, so as to leave the connections to the rear intact in case you ever wanted to reestablish the OEM sensor.

 

Just curious nh70, what value potentiometer would you use for the optional fix you mention?

 

Post #13 indicates that 3.9K is the total resistance required, so a 5K linear taper variable resistor with a 20K fixed resistor in parallel would yield 4K total resistance.

 

Yep. I saw that, I was just checking to see if for some reason there needed to be different values when tapping in at H12.
Thanks!