I recently bought a 2000 S500. When you first get in and turn the key, the wipers start automatically. Once they go through their cycle, they stop but not in their resting position. They pretty much stop where they want. The same thing happens when I actually use them when it's raining or cleaning the windshield. Has anyone else had this problem? Could it be a bad wiper relay? Any help would be appreciate.

 

Rain sensing wipers will sometimes cycle once when you start the car. They are activated when the wiper switch is in the first position. IF you turn the switch all the way off, then they should not do anything when you start the car. If they do, then you have something going on with your switch.

IF this happens only when you have R/S active, And you are sure your windshield is clean around the sensing area, you either have a bad R/S module OR someone installed a new windshield and either broke the R/S harness, or installed the wrong windshield.

IF they however, fail to stop in the resting position at any time, then the relay is bad.

 

+1!

I myself experienced the "wipe on engine start" sometimes. But only if I forgot to switch it off after the last rain (rain stopped before killing the engine, thus me forgetting to switch off the wiper properly). Next time I start the engine, the wiper will wipe once, but returns to the resting position afterwards. Then I normally switch it off (gets annoying to wipe a dry windshield).

So, I fully agree, that if it doesn't return to the resting position, there is something wrong with either the system (i.e. relay) or the windshield and its functions.

 

In the early W220 models, the wipers always cycle through everytime you start the car if you leave it in position one. The only way to stop that is to switch the auto wipers off. In the later models, that first cycle was finally eliminated and yes it sometimes cycles but not in most cases. In warm days though you do get the wipers come on as you drive for no reason. As far as the wipers stoping anywhere, you may have a bad wiper motor.

 

Where is the relay located?

 

I'm glad to hear that the cycling on hot days is not just my car. Mine will cycle once on start, and if the car has been sitting in the sun for a while (my work parking is out doors) it will cycle periodically-once every two minutes or so--until the AC cools the WS off from the inside. I just turn the auto function off. It only happens to me on hot days.

 

All,

Any feedback on the relay location?