Windshield Rain Sensor

[FireTumbleweed]

Is it possible to replace a windshield without replacing the rain sensor box? I've had my windshield replaced a couple time in the past and I don't remember it being replaced ($200+ item!). I'm trying the dealer this time and they state they usually replace it during the windshield install.

I thought the OEM windshields come with the "sticky foil" attached to the windshield already and one only has to attached the sensor box taken from the old one to this "sticky foil".

Anybody have experience in this? Thanks.

[Joe///540i]

The sensors for both rain and light are on the back of your rear view mirror. The new windshield will have a plate in that area where the mirror reattaches to.

[JimLev]

They are trying to up sell you on parts you don't need.
All you need is the windshield for rain sensing, it will have the metal clips (plate) already attached to it like Joe mentioned.
Might want a new rubber gasket too.

[Joe///540i]

Might want a new rubber gasket too.

Oh yeah, very important, make sure they use an OEM seal and if not it will look horrible and create wind noise. Pay extra for it. Other considerations - replace the left and right cowls and the wind screen cowl (the plate behind where the wipers attach to the motors). Do it all while you are in there. The cowls, screen and OEM seal cost me around an extra $125 or so.

[FireTumbleweed]

I'll already pre-bought the windshield, rubber seal and adhesive from the parts dept. I can get them to match prices. I replaced the left and right cowls a couple of years ago myself and they are still ok and the main cowl still looks good but will replace myself if anything happens.

So to confirm on the windshield, there is no "adhesive" that the box attaches to. I've looked at it under the mirror after an install and saw the box

https://www.fcpeuro.com/products/bmw...or-61356923954 attached to the windshield.

Jim,Joe your saying that box clips onto a metal plate which comes pre-attached to to the windshield and is easily removable. I wonder if that is a standard blah blah they say because 2 sep guys (at different times) said it was needed. Wonder of some models you actually have to do that. I've replaced the windshield 4 times since owning and never have been billed for one. I even mentioned the price of the part and they didn't get off their story of it being needed.

[Joe///540i]

Hmmm...I am not completely following what you are trying to remove. You or the installers pop the mirror off the glass. The mirror is the "box" with sensors that clips onto and lines up with a windshield "plate" for lack of better words.

[FireTumbleweed]

I'm just trying to understand the mechanics of it as the SA really doesn't seem to know much. The part I linked (FCP) is what I have seen attached to the windshield after removing the plastic cover at the base of the mirror. I popped off the cover a few years back I was curious. I saw the linked (FCP) part and originally thought it was held on with some type of adhesive, but it sound like it is held onto the window mechanically?

Update: Actually just found a DIY online with pictures. Look like the part I linked to (FCP) attaches to the metal plate/bubble/optic thingy which should come already attached to the windshield as you and Jim stated. The part linked attaches by means of plastic tabs. I just had trouble visualizing what that plate looked like and how the "sensor" attaches to it.

I hate going to dealers but all the local installers never seemed to care about proper depth setting of the windshield into the frame so I figured I'd gamble on the only local dealer that has techs onsite vs third party. I went through my expectations and how I want to see the depth when I picked it up measured with that square tool thingy the TIS talks about. Now just gotta remember where I found the correct depth spec.

[Joe///540i]

I'm just trying to understand the mechanics of it as the SA really doesn't seem to know much. The part I linked (FCP) is what I have seen attached to the windshield after removing the plastic cover at the base of the mirror. I popped off the cover a few years back I was curious. I saw the linked (FCP) part and originally thought it was held on with some type of adhesive, but it sound like it is held onto the window mechanically?

Update: Actually just found a DIY online with pictures. Look like the part I linked to (FCP) attaches to the metal plate/bubble/optic thingy which should come already attached to the windshield as you and Jim stated. The part linked attaches by means of plastic tabs. I just had trouble visualizing what that plate looked like and how the "sensor" attaches to it.

I hate going to dealers but all the local installers never seemed to care about proper depth setting of the windshield into the frame so I figured I'd gamble on the only local dealer that has techs onsite vs third party. I went through my expectations and how I want to see the depth when I picked it up measured with that square tool thingy the TIS talks about. Now just gotta remember where I found the correct depth spec.

Understood. I like doing all my homework too even when I’m not doing the work. Hopefully Jim and I were helpful. The windshield and mirror sensors are plug and play.

I’d focus more on the installer, the seals, cowls and adhesive removal and reapplication

[computiNATEor]

I knocked the plate off my windshield with my elbow in my black car (before it was totaled) when vacuuming the interior at one point. Auto shops sell rear view mirror adhesives that will fix it.

[rdl]

Is it possible to replace a windshield without replacing the rain sensor box? I've had my windshield replaced a couple time in the past and I don't remember it being replaced ($200+ item!). I'm trying the dealer this time and they state they usually replace it during the windshield install.

I thought the OEM windshields come with the "sticky foil" attached to the windshield already and one only has to attached the sensor box taken from the old one to this "sticky foil".

Anybody have experience in this? Thanks.

I'm assuming your title block listing a MY 2002 car is accurate. Earlier years up to around 1999 used a different system named AIC that did not include automatic headlight control. Same idea, just a different sensor module and prism on the windshield.

The RLS module or sensor box does not need to be replaced with a new windshield. You're quite right that the old RLS sensor is simply attached to the prism (I assume that's what you mean by "sticky foil") that comes with the new windshield. Been there, done that.

Note though that when either a new or re-used RLS module is first installed on a windshield it must be re-initialized using diagnostic software. If the re-initialization isn't performed there is a good chance that the rain sensing won't function properly.

See the image for what an E39 RLS windshield should look like. A non-RLS windshield won't have the prism.
The prism directs the infra-red light the RLS uses to sense water on the glass. It also has lugs used to attach RLS module.
The mirror mount is the attachment point for the mirror and is entirely separate from the prism.
The mask is the blackout paint on the windshield for appearances.

MirrorMountImage.jpg

[Joe///540i]

I'm assuming your title block listing a MY 2002 car is accurate. Earlier years up to around 1999 used a different system named AIC that did not include automatic headlight control. Same idea, just a different sensor module and prism on the windshield.

The RLS module or sensor box does not need to be replaced with a new windshield. You're quite right that the old RLS sensor is simply attached to the prism (I assume that's what you mean by "sticky foil") that comes with the new windshield. Been there, done that.

Note though that when either a new or re-used RLS module is first installed on a windshield it must be re-initialized using diagnostic software. If the re-initialization isn't performed there is a good chance that the rain sensing won't function properly.

See the image for what an E39 RLS windshield should look like. A non-RLS windshield won't have the prism.
The prism directs the infra-red light the RLS uses to sense water on the glass. It also has lugs used to attach RLS module.
The mirror mount is the attachment point for the mirror and is entirely separate from the prism.
The mask is the blackout paint on the windshield for appearances.

MirrorMountImage.jpg

I’m not sure you’re right about it having to be reinitialized. I just had my windshield replaced twice in one week and stood over the installers. He told me it only needs to be reinitialized if you turn the key or start the car while the mirror is unplugged. I almost did this during the install and he caught me before I did and told me this.

All my sensors are working fine.

[rdl]

I’m not sure you’re right about it having to be reinitialized. I just had my windshield replaced twice in one week and stood over the installers. He told me it only needs to be reinitialized if you turn the key or start the car while the mirror is unplugged. I almost did this during the install and he caught me before I did and told me this.

All my sensors are working fine.

One may get away without re-initializing, but I think it becomes a crap shoot if the rain sensor will be properly calibrated and not too sensitive or not sensitive enough to mist on the windshield.

TIS is explicit in its instructions to re-initialize (or initialize) whether installing a new, virgin, RLS or reusing an old one.

BMW tech docs describe that the RLS has a learning function that adapts its response as the glass ages. One presumes by aging they mean the tiny micro pitting from road dirt that will change the reflectivity off the glass surface that the RLS uses to sense water on the windshield. Consider for instance the difference between an elderly windshield so pitted one is blinded driving into the sun compared to a brand new flawless windshield. Or the different windshield options, e.g. tint levels & or solar. The re-initialization is supposed to reset the module to a new starting point based on that particular windshield.

Perhaps the advice from your installer is a mis-conception taking only part of the instruction set. IIRC, the sequence involves:
- clean the windshield over the prism thoroughly of all dirt, grime, oil and wax
- connect to the RLS with the diagnostic system
- click on the "reset" button
- leave the key in position 1 (or 2, not sure which) without starting the engine or changing the wiper stalk for 20 seconds
- turn the key to "off"
- then start the engine. The RLS should be correctly calibrated

[FireTumbleweed]

Thanks RDL, yes that is exactly what it looked like (yes it's a 2002). RE: Headlight control. If your talking automatic on off, yes I have that.

I'll be sure to mention my expectations regarding re-initialization to SA. Is this the TIS you are referring to?

https://www.newtis.info/tisv2/a/en/e...odules/E1aWle0

[rdl]

...
Is this the TIS you are referring to?

https://www.newtis.info/tisv2/a/en/e...odules/E1aWle0

Yes that's the TIS instruction.

My recollection of the initialization sequence in post #12 above was faulty.
I found this sequence below in an old post written at the time.

1) reinitialize using INPA, DIS, etc., which requires the key to be in the "run" position
2) turn the key off
3) set wiper switch to "off", i.e. NOT in the intermittent, speed 1 or speed 2 position
4) turn the key to "run" and wait 10 seconds
5) adaptation to the w/s is now complete
Instructions I've seen are silent on the issue of auto light switch position.

[Joe///540i]

Yes that's the TIS instruction.

My recollection of the initialization sequence in post #12 above was faulty.
I found this sequence below in an old post written at the time.

1) reinitialize using INPA, DIS, etc., which requires the key to be in the "run" position
2) turn the key off
3) set wiper switch to "off", i.e. NOT in the intermittent, speed 1 or speed 2 position
4) turn the key to "run" and wait 10 seconds
5) adaptation to the w/s is now complete
Instructions I've seen are silent on the issue of auto light switch position.

So what does this initialization or calibration result in? Better at sensing rain drop count and wipers speed? I will give this a shot for the hell of it but I am not expecting to see any difference. They are working fine at two new windshields but I will report back.

Question - ket position "run" is not with the car running correct?

EDIT - check that, I can't do this part, don't have one:

• Connect BMW diagnosis system

[rdl]

So what does this initialization or calibration result in? Better at sensing rain drop count and wipers speed? I will give this a shot for the hell of it but I am not expecting to see any difference. They are working fine at two new windshields but I will report back.

Question - ket position "run" is not with the car running correct?

EDIT - check that, I can't do this part, don't have one:

• Connect BMW diagnosis system

Initialization sets the reference level for a dry windshield and the RLS is then able to determine how wet the windshield is.

The RLS shines beams of infrared light through the windshield glass and measures the reflection back from the surface. Maximum reflection occurs with a dry windshield. As water accumulates, the reflection back to the RLS's sensor is reduced depending on how much surface area is covered by water. At a reflection signal strength corresponding to a little but not too much reduction, i.e. a few droplets but not too many, the RLS triggers a wiper sweep. But micro pits on the glass also reduces the reflection which would yield the same result as a false wet signal. So to decide when the signal is low enough to trigger a wiper sweep, the RLS must know what strength signal corresponds to a dry windshield. Initialization teaches the RLS what that reference signal strength is.

The initialization step is done with key on engine off.

[computiNATEor]

Initialization sets the reference level for a dry windshield and the RLS is then able to determine how wet the windshield is.

The RLS shines beams of infrared light through the windshield glass and measures the reflection back from the surface. Maximum reflection occurs with a dry windshield. As water accumulates, the reflection back to the RLS's sensor is reduced depending on how much surface area is covered by water. At a reflection signal strength corresponding to a little but not too much reduction, i.e. a few droplets but not too many, the RLS triggers a wiper sweep. But micro pits on the glass also reduces the reflection which would yield the same result as a false wet signal. So to decide when the signal is low enough to trigger a wiper sweep, the RLS must know what strength signal corresponds to a dry windshield. Initialization teaches the RLS what that reference signal strength is.

The initialization step is done with key on engine off.

Good to know, thanks!