# Retrofit Rain-Light-Sensor (S521) without additional Parts!



## sebi04.04 (Nov 10, 2013)

Since my car had relatively less lightning options by factory, but was equipped with a lot of multimedia & driving assistance Options i was planning to retrofit the RLS by swapping the needed parts anyway.

While coding my car i came through a lot of functions related to the RLS, where it said "verbaut" but obviously it was not working, i don't even have the light switch position "Auto". So i searched a way to figure out if the sensor is indeed equipped and working. found that way and was able to retrofit the RLS without (in my case) swapping any of the parts. :thumbup:

*This writeup maybe helpful for some of you owning a F20 & F30, with relatively low equipped light options but high driving assistance options. *

I believe this retrofit was possible because i have the KAFAS2 Camera in my windscreen for SLI. Maybe BMW does delivier these kind of option only with a RLS pre-equipped. My second guess is that i have the RLS equipped but not activated because of the 6WA extendend instrument cluster: I found some settings related to the RLS in KOMBI-ECU which seem to be responsible for Dimming.

I have the following options on my Car:

(6WA) Extendend Instrument Cluster
(8TH) Speed Limit Info
Normal Halogen Headlights

*How can you tell if RLS is equipped but not activated ?*
All Pics are German 

Open Rheingold / ISTA-D and choose "complete identification".










Switch to "Vehicle Information", then "ECU-List" and highlight the FEM module by clicking on it. Then hit "show ECU-Functions"










FEM Options will open and hit the second Tab ("Diagnose-Abfrage" in my case). Then search for RLS related entry ("Regen-Licht-Solar-Beschlagsensor" in my case).










You can now select desired options and then read out the live data from the vehicle fitting that entry. I selected "Fahrlichtsensor" for 2 different Values given out by the Light Sensor, "Regensensor" for a value of Rain-Detection, "Verbau Fahrlichtsensor" & "Verbau Regensensor" for checking if the RLS is equipped.










If equipped and working, there have to be Values on the live check. When pouring water on the windscreen the value changes, when holding a flashlight over the sensor, the value is changing for the lux. Also it should state "verbaut" with both sensors.










If everything is similar to my values, you can go on with the coding and manipulating the Light Switch. I used the RLSBS Retrofit.pdf from another user to disassemble and manipulate the Switch:

http://f30.bimmerpost.com/forums/showthread.php?t=970448

Basicaly it's just pulling the switch knob of with gentle force, and cutting one plastic restrainer with a knive or similar, to enable the knob to rotate to the left when it is on "0". You can check that out in the .pdf document and the picture below.

Photo of my KAFAS2 with the RLS equipped but not active by factory.










Photo of my light switch after modification, you can see that there is no "Auto" Mark, but the knob stands on this position.










Here are the codes for activating the RLS, code with E-SYS:

*All Codes in FEM*

*FLC_AKTIV set to aktiv
RLS_DEF_FLC_SCHWELLWERT_SATZ set to normal* (changed to un_empfindlich in my case, set whatever you like: it is the sensivity of the light-sensor)
*WW_REGENSENSOR set to RLS_verbaut*
*AIC_KOMPRESSOR_MAG_KUPPLUNG set to aktiv* (Note: Since i have no Automatic Climate in my car, setting "aktiv" lead to a mistake in the Car, leave it set to "nicht_aktiv" if you have simple climate Equipment)
*RLS_LIN_VAR set to RLS
REGENSENSOR_INTERVALL set to nicht_aktiv
*

Note that the auto light sensitivity is depended upon you: 
Un_empfindlich = not sensitive (turn on when less light, best for me)
Normal = normal sensitivity
Empfindlich = sensitive
Sehr_empfindlich = very sensitive (turn on even under sun light)
Tagfahrlicht = Not tested yet (at least by me)

When Coding has been done, start the car and test everything 

There are good instructions for testing the functions in the .pdf, better than i could ever write this up. 

Everything was a little surprise for me, i thought i had to order different parts for achieving this. I hope a few of you can benefit from this, too. :thumbup:


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## shawnsheridan (Jan 10, 2009)

Interesting. Nice detailed write up, and thanks for sharing it. :thumbup:


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