RWagz

Hi there. A forum search didn't turn up anything related.

My intermittent wipers work fine for a random while until they run continuously and speed up on their own, often/likely due to there being more rain to clear.

The problem is that it does not slow back down or go back to being intermittent despite the rain letting up and the windshield being clear. I have to turn the wipers off then back on again and it starts working as expected - slowly and intermittently.

I have replaced the wipers, ensured they are the right size, and I have cleaned the windshield. I can't think of anything simple to try before replacing sensors and maybe control modules.

For now I'm using the manual intermittent mist function.

Does anybody have recommendations?

konigstiger

Visually inspect sensor if all looks fine may need re-initiation or replacement only way to tell is pull codes. Part #s used 2048708826, 2049017801, and current/new 2049014504.

CaliBenzDriver

The windshield optical sensors sends serial data to the F-SAM computer that manages power to your wipers.


At some point in all your troubleshooting, consider "a car reboot" by simply disconnecting batteries for 15mn.

This will refresh the silly control unit. It will help prevent battery drain when it fails to enter low-power mode ie. deep sleep.

S-Prihadi

I once experimented on auto wiper speed by using garden hose to spray the windshield middle top sensor as Mr K document showed.
It works, more water spray, more wiper speed.

Aside from Cali's advice to reboot the system, do this :
Take a bright flashlight and see if you have debris at that rain sensor. If any debris there, sensor may think it is "raining".
Shine from outside to inside, its just a very dark tinted glass only.

Often debris can come from the grey foam MB uses to cut down wire vibration noise.
These foam for my car, a few have crumbled into dust, example the one at my panoroof control and it does make annoying micro vibration sound at the right
resonance frequency.

atraudes

I'm interested in what you find too. Mine work completely as expected until they've been running for a while. Then, at some random point (usually when the rain has slowed to a few drops or altogether) it'll go wild and wipe as fast as it can and won't stop. Turn it off and back to auto, it goes back to normal. I figured that's just the way they were but if a new module fixed it I'd spring for one.

CaliBenzDriver

Something is driving this DISTRIBUTED SYSTEM nuts!

At list the command Reset (Auto > Off > Auto) is a perfect workaround! 👏

We recall the Rain/Light sensor uses solderless pins. If you haven't done so take a closer look at that module. Some people found luck right in there.

In California it only rains once a year so my wipers are seldom activated. I had to rework my wobbly wipers early on. The skipping vibrations were so bad, the finger tight aluminum nut of the driver arm got loose and started to shave the alloy splines.

The rain sensor module is a small LIN peripheral of the busy OCP controller. From there the data is interfaced with F-SAM that powers the windshield wiper gear.

If you have a scanner handy, check that you can read ALL live data slots of OCP. Module may be alive but not showing data (It does runs with both LIN + CAN).

A scanner may provide you with archived faults for random glitches. Marginal voltage is a well organized source of chaos.

Last we shouldn't ignore the messaging from the wiper mode stalk travels through the steering column modules.
This stack feature solderless pins from steering buttons all the way down the multiple modules sandwich.
Just because the turn signal stalk works okay is no guarantee the wipers stalk won't use different signaling. Multiple equipment suppliers build these sub-assemblies components.

Try to SCAN and troubleshoot clues to help you save good parts.