My blade will move across the windshield from drivers to passangers side just fine, but when it starts to come back it will stop, make a whirring sound, and I will have to move it by hand to get it back to the stop position... Is it possible that something is wrong with just the motor or could it be the transmission linkage...
There are 2 possible reasons for your fault;
Either you have stripped nylon gear inside the wiper motor gear box as in above picture… new motor required.
You have a loose nut on the rear of the wiper mechanism, either nut 1 or nut 2 in picture below is loose … adjustment required.
To determine what is the problem you should recreate the fault by running the wiper until it sticks/stops again, as follows;
1… turn on the wiper to position 2, which is normal speed.
2… when the blade stops on the way back from the passenger side, immediately remove the ignition key.
3… turn the wiper switch to 0, which is OFF.
4… remove the windscreen trim to get access to the wiper motor as in picture below.
5… remove the motor gear box cover... with the word ” Germany” written on it... and inspect the teeth on the nylon gear that are close to the worm drive, any “shavings” as depicted in the picture below will mean that you will need to replace the motor.
6… if there is no damage to the nylon gear and it is in good condition like the one pictured above then there is nothing wrong with the motor and your fault must be a loose nut on the rear of the mechanism, either nut 1 or nut 2 as pictured below.
Either you need a new motor or you need to realign the existing mechanism and tighten up the nuts 1 and 2 as pictured above. In either case, whether fitting a new motor or adjusting an existing mechanism/motor, ensure the motor is in its park position.
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In your particular case... and if you need a new motor… then this is the one you need… if the part number matches your existing motor? Mercedes Benz W202 C230 C280 C43 - Wiper Motor 98-00 - eBay (item 390170321271 end time Mar-10-11 10:50:41 PST)