I ordered a new rain light sensor from FCP Euro and it does not fit, the port and plug do not match. FCP said it was a genuine part and I put my vehicle info in when I ordered it (though in retrospect it did not include fitment information), so I'm confused. Maybe I should've ordered directly from MBUSA? Photos attached if anyone knows the correct part number I would appreciate it. The part I ordered was 204-901-45-04, which is the number listed on the MBUSA parts site and FCP Euro for the rain and light sensor..


New part installed, with a white port with a ridge on the right and the original blue plug with the ridge on the left that will obviously not fit.

Original part with a blue port with a slot on the left that fits with the original blue plug ridge on the left.

 

Whats your vin # ?

 

There should be a sticker on the old sensor with the part number. I looked up all 3 currently listed sensors and they all have the same white connector port.

Some searching around on ebay and I found one with that blue connector. Its not a 204# though.

 

I was so bitter I neglected to check the sticker on the original part. I just did and it is 207-820-34-26, which mbparts.mbusa.com says has been replaced by 207-901-37-00, which according to the website WILL NOT FIT MY CAR. Meanwhile, the part that is supposed to fit...does not fit. Something similar happened when I needed the clock spring replaced, the correct part was not easily evident on the website even though I was searching using my specific vehicle info-- a local dealership told me a different part number and replaced it. So...it all seems like a conspiracy to get me to a dealership service center.

 

Hopefully you can return the sensor after telling them the issue. I doubt there is any way that FCP would have figured out to send you the 207 # sensor. They would have looked up your vin and seen the same diagram sheet i posted above. I got the 2010 submodel from an eBay listing.






So its not just your car. Just an fyi theres quite a few sensors on ebay cheap.

 

I entered the actual part number for the failed (?) light/rain sensor in my vehicle and Mercedes-Benz parts said it was replaced by another part number which I ordered from auto parts nation. The original blue plug matched the new part’s blue outlet – blue with three pins inside in the right configuration — so I installed the part and when I started the car got an immediate “auto lamp function inoperative” message. Oddly when I use a code reader it doesn’t display an error code, even though it is reading my VIN number accurately. so I’m not sure if it’s faulty wiring, a bad replacement part, a redesign part that simply doesn’t work in my 2010 vehicle, a fuse, etc. If anyone has any ideas, please share as I’ve now ordered two parts, neither of which solved the problem

 

According to Pelican Parts article it may require calibration from a Mercedes scanner.

https://www.pelicanparts.com/techart...eplacement.htm

Is the auto lamp feature not working at all? Have you gone into the menus and played with the settings to double check? Also maybe it will just take the car some time to calibrate it on its own, similar to new tpms when first installed.

 

Auto lamp feature was working intermittently before I changed the part. Rain sensor has not worked for quite some time.

 

I put the new part back in and when I started the car immediately got the "auto lamp function inoperative" message. Decided to leave it in and see what happened. Surprisingly, the the rain sensor started working again right away, while the lights would just stay on if I put them in the auto position no matter how bright the sun -- so I'm stopping by the mechanic today to see if calibration with a Mercedes scanner gets the auto lamp function to work.

 

Mechanic calibrated with MB scanner, now it works!

 

Same problem, so I bought a cheeep one from Aliexpress claiming it is an updated part plus correct for my vehicle BUT Aliexpress is warning me it needs "registering" meaning a SUN diagnostic or XENTRY. My iCarsoft MB II may not be able to do it. Problem is that Merc stealerships want AUS$300 just for one fault to give a quote, not even fixing it! Lucky that fault is only intermittent, so hopefully it does not come up during the test drive with a buyer?

 

I went and cried to my mechanic that I tried to do it myself after watching a YouTube video and it didn't work so since he just did a bunch of work he took care of it, but he took like half an hour of fiddling with the scanner to get it to work.

 

These optical sensors require calibration setting to match them to the windshield type in use on your chassis type.

They are quite "sensitive" to disturbances by nature.

They provide night/day signal for headlights and rain signal to wipe windshield and close sunroof.

They are built with pressed-pins that work ok for a while given low vibrations. That can be soldered to be reliable.