Wiper slow and jerky 300E
 

My 91 300E just began having wiping problems. Runs on intermittent, slow and fast OK in the beginning. After running for a while it begins to slow and get jerking. Has not totally stopped but make me feel like it could totally fail at any time. Any ideas before I tear into this problem? Thanks for all input you may have.

Clean the windshield really well with Meguiar's Paint Cleaner, or a similar product, then apply Rain-X.

I will try cleaning and RainX but I have had this car for 18 years and never experienced this problem before. It concerns me that I could get stuck in the rain/snow and have total failure. I checked fuse and cleaned the ends. Tried to remove the combination relay but could not pull it out. Is there a trick to removing the relays? I thought maybe the relay contacts could be burned and not making good contact after operating for a time. I first thought the slow down was related to the rain lighting up and the resistance of the dry windshield, it slows down even with continued rain after 20 minutes of operation.

I had the same problem with a 89 260E. I got it to work better by oiling (transmission fluid) the shaft that the wiper attaches to but it will eventually have to be completely disassembled, cleaned and re-greased. That includes the motor as well. The grease is now over 20 years old and needs to be replaced.

Thanks for the input. I'm afraid to ask, but how do I access the shaft and motor?

Better get to it soon. That binding will only go for a short while, then the nylon gears will strip, and you will have a way more $$$$ repair.

There's youtubes showing how to get at the sliding rod parts for re-greasing. this is for a c-class but it's similar I think:

how to remove Mercedes w202 windshield wiper motor assembly and lube - YouTube

Thank you for the utube post. Just finished watching. Two questions: What type of grease do I use? From what I saw the lubrication is only under the turtle cover. Is this correct? If so, then no need to remove the entire assembly, right? Many thanks, I find it very interesting that someone will take the time and effort to help others. I have used video's from others for Mercedes and Porsche projects in the past with great success. I didn't even think to do a web search for this issue.

Do the re-greasing on the sliding parts under the cover for a start...if it doesn't rectify the issue there is a more involved process of looking at the motor and bits that wear out there.

I think the job can be done with white lithium-type grease, but doubtlessly you can get a real $$$ tube at the dealer, If you prefer

I'm going to give Amsoil Arctic Synthetic Grease a try when I do mine. Temperatures here can go down to -35 C so I want something that isn't going to stiffen up.

Just completed the relub job. Now I need a good rain to see it is fixed. I did not service the motor, so if the problem continues I know the next step. The utube videos helped but there is a difference in my assembly and the one shown. Biggest problem was the setting of the stroke so that the blade was retracted at the 12 oclock position. Now it will be easy to do if I have to get back in there for the motor. Thanks for all the help.