[bullockandrew]

Hi,

My rain sensing wipers have started acting up. Initially on the I setting, they seem to work in light rain and then suddenly they speed up to a constant, so switching between I and II has no effect - even if the rain has stopped. Sometime if I switch off the ignition and start again they start working normally - and then after a short time the problem returns.

Anyone know why this is happening?

 

[jjrodger]

Something similar happens to me. In very light rain, the wiper works fine for a short while on setting I, but then starts to run too frequently. I think it is because when the rain is very light, a greasy film builds up on the screen, confusing the rain sensor. I find that after cleaning the screen with the washers, the wiper returns to normal for a few minutes... until the film builds up again. Recently I have taken to changing the wiper blade every six months or so, perhaps even more often. This has made a big difference. The blades seem to wear out very quickly, and a fresh blade seems to be much more efficient. They are not cheap, a little under 30quid.

 

[bullockandrew]

Thanks for that - I have exactly the same problems you describe. I'll try a proper clean and a new blade.

 

[jjrodger]

The other thing I do is to deal with light rain using the flick switch function: not particularly satisfactory given the car has a rain sensor. This defficiency is a real shame because otherwise I find the rain sensor works really well, generally getting the frequency of wipes just right.

 

[IRLCK]

Hi Andrew,

I posted something similar a while back, my 320 wipers are such a pain sometimes. I was driving to work this morning and there was a very light rainfall. The wipers were ok at first, but then intermittently would wipe 4 or 5 times as if on Setting II, then stop. This pattern would repeat itself every few minutes. I feel the issue is caused by a greasy film over the rain sensor as JJ suggests. I have a new wiper blade which I'm going to fit this week and I'll try to clean the windscreen as best as possible and see what happens.

 

[Corkscrew]

Rainex works for me. I think it keeps the windows clean so that the gop that interferes with the rain sensor doesn't have a chance to build up.

Also, I wash the cars at least once a week.

 

[jjrodger]

I keep meaning to try Rainex, I have only heard good things, let us know how you get on.

 

[bullockandrew]

All great advice. I was wondering if it had anything to do with the fact my windscreen was replaced last year. Or whether it was an electrical gremlin. One follows another in my car!

 

[herb]

Where is the rain sensor located?

 

[jjrodger]

ahead of the interior rear view mirror, top-middle of the windscreen.

 

[GregDickson]

ahead of the interior rear view mirror, top-middle of the windscreen.

I have a 1993 SL600-can anyone tell me when the sensor began to be installed? Thanks.

 

[ErikFinn]

I have a 1993 SL600-can anyone tell me when the sensor began to be installed? Thanks.

According to Ken as of 1997:
Mercedes SL500 R129 1990s History