Wiper motor, a critical but often neglected part

[jftu105]

It has been raining lately and when I needed it the most, the windshield wiper became slow and lethargic. Then I smelled some burned plastic smell. Alarmed, I shut off the windshield wiper but it was raining, luckily light. I was able to drive without using it. Arrived home and checked closely. There was a strong burned smell from the wiper motor. Removed it and measured the coil resistance, only 2 ohms instead of 12 ohm of my other cars. So it was burned due to too much current. Went to a local yard and got a replacement. In the mean time, ordered a new VEMO wiper motor off eBay for $77 as a spare. Put the one from yard in but the wiper was still slow. Sprayed some lubricant over all the joints but no improvement. Finally, I realized the the wiper shaft, which pushes in and out during wiping, was causing the problem. Sprayed some healthy MOS2 lubricant over the shaft and that was it. Now, it wipes back and forth quickly without issues.

So, this is what I think an often neglected but critical issue when raining. Make sure that you lubricate the joints of the wiper mechanism, in particular the wiper shaft. You simply open the cover of the wiper and spray some health lubricant. I then did it to all my cars (five of them).

If you cannot see you cannot drive in the rain. Do yourself a favor and lubricate your wiper mechanism so that you don't burn your wiper motor. Stay safe if you are traveling during the Holidays and do this critical maintenance before your trip.

jftu105

 

[gsxr]

I had a similar experience a few years ago on one of my daily drivers (forget which car). The wiper was moving very, very slowly and was nearly useless. I didn't get the burning smell, I may have shut the wipers off before it got that bad.

Anyway - I also thought the wiper motor or mechanism was defective, or at least in the process of failing. For some reason I figured I'd try spraying lube on the round shaft which slides in & out. Voila... problem was cured instantly, wiper went to full speed, and I never had another problem with it. This may have been on a car that was parked for years without the wiper being used.

Definitely a good idea to lube this area periodically!

 

[jftu105]

Now, I think about it. The 1994 wiper motor has a diode soldered across the input lines of the dc motor, while the one from a 1992 (in a yard) does not. The resistance of the coil measured with the one from 1992 is about 12 ohms, while the one with 1994 (with a heavy burn smell) is 2 ohms. This 2 ohms reading perhas is misleading due to the diode. I reversed the polarity in measurement and still got the same reading (strange). It is likely, with the wiper shaft fully lubricated, that the "burned" motor would still work just fine as in the case of gsxr. I will not try that as I have put everything back. I don't want to cut the wire to do the measurement either. I will wait until the new VEMO motor to arrive and do a comparison. The diode is used to suppress some back EMF when the motor stop or reverse to extend the motor life. The one from a 1992 300E (with 160,000 miles) is still doing fine without a diode. So much for the theory of the diode.

jftu105

 

[jftu105]

The 1992 wiper motor turned out not suitable for the 1994. At high speeds, it burned out. The fuse #2 also burned. Put in the new Vemo wiper motor and everything back to normal. The 1992 wiper motor does not have a diode across the motor coil. As a result, at high speed operation, the back EMF is not suppressed and the coil burned. The impedance through the coil reads 1 ohm, while the new motor reads 25 ohm.

jftu105

 

[rayhennig]

We fitted a new (genuine MB) motor recently after a complete overhaul of the mechanism, including "new" gears from a selection of 20+ 124s in a field!

Result, excellent aside from the fact that the sweep is very slightly too far to the right, when looking at it from the front of the car. Too far left when inside the car. The upshot is that the blade gets to the end of its sweep to the left (from inside) and twitches up 1.5 cm before resting. Annoying but not a disaster.

Do you think we didn't set the "settled" position correctly before engaging the motor? That seems logical to me.

Any ideas?

Best to all.

RayH

 

[r44raven]

I remember deconstructing the wiper mechanism on my 500 some while back for a thorough cleaning/lubrication - and recall it being a bit of a nightmare getting the sweep/park positions correct afterwards. @JC220 is the expert in this field? I seem to recall you can "mark up" the components before pulling everything apart, to make sure it all works OK on re-assembly? Joe?

 

[rayhennig]

I remember deconstructing the wiper mechanism on my 500 some while back for a thorough cleaning/lubrication - and recall it being a bit of a nightmare getting the sweep/park positions correct afterwards. @JC220 is the expert in this field? I seem to recall you can "mark up" the components before pulling everything apart, to make sure it all works OK on re-assembly? Joe?

Yes, thanks. I did have some advice from @JC220 and shall be bearing that in mind when I finally get to investigating further.

Real life is retarding my efforts with the car.

R

 

[dionphaneuf]

I have an earlier car with the earlier/harder to service/lube mechanism and it failed on me last year. I ought to order another motor lest we have another deluge like the Bay got this last weekend. That said, the new motor seems strong. As for park positioning, I marked my old one on removal and it seemed to go back in fine.

 

[rayhennig]

As for park positioning, I marked my old one on removal and it seemed to go back in fine.

That is what we may have failed to do. It was late on a Sunday after a few beers.

R

 

[T0Pnotch55]

anyone know the part number or where can i order this clamp?

 

[gsxr]

anyone know the part number or where can i order this clamp?

P/N A1249800084... but possibly NLA. You'll need to call a dealership and ask about worldwide inventory. Only $4 MSRP if available.

 

[T0Pnotch55]

P/N A1249800084... but possibly NLA. You'll need to call a dealership and ask about worldwide inventory. Only $4 MSRP if available.

thank you very much