I pulled out the blower motor on my 1980 300TD. I'm not sure if it is a Bosch unit or not there was no manufacturer name stamped on it. I had to file the staked areas around the rim of the can to get the back cover off. The brushes were well worn so I set about to replace them. They measured 5/16" square and had coil springs behind them. I don't have an ACE hardware store nearby so I went to TrueValue. They had a box labeled carbon brushes but they all were no thicker than 1/4". I ended up with 1/4 x 5/16 brushes each with their own spring. I glued a 1/16 aluminum shim to the bottom side of each brush holder to make up the difference. This was in the width direction so the diametrical contact would be the same. The brush holders are offset by a half 1/2 brush width so a corner of a flat brush face would contact the commutator. Not an idea situation. I have a small milling machine so I cut the brush to get the profile and length right. I also have a lathe so turned the commutator. For some reason it wore into a conical shape and was heavily groved so this really improved things. I had to use the smaller diameter springs that came with the brushes so I cut them to the same length. The spring rates seemed to be about the same. I soaked the bushings in the can and end cover in heated AT fluid for several hours to try and get the porous metal to soak up more oil. I assembled everything back and added some additional shims to take out some end play. When I hooked it up to my 12V power supply it seemed to run faster and quieter than before so I am pretty pleased. We got about a foot of snow today so I have to dig out the car to put the fan back in. I would also like to check out the resistors that control the fan speed can someone tell me were they are located?

Thanks

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Bill Reimels
Now down to one:
1972 300SE 3.5 W109 (Euro delivery)

Hi Bill --

I suspect that all the brushes the corner hardware store sells are made for a 110-volt AC motor vs. a 12-volt DC motor, which is obviously what you have. If they work for you, that's great. But I was just directed on another list to the website of a vendor who sells all sorts of brushes, including some that are made for automotive applications: http://www.carbonbrush.com/brushes.htm

I recently rehabbed a blower motor using brushes from a factory in Milwaukee called Schunk Graphite Technology (a subsidiary of the Schunk Group in Germany). They wouldn't talk to me unless I bought $100 or more of product, but they delivered quality 12V brushes for $4.17 each that fit the Bosch motor like they were factory-installed. I sold my surplus 22 brushes to folks on this forum and diesel.mbz.org.

The point being, I have the invoice from Schunk in front of me describing the brushes they sold me as .312-by-.312-by-.75 inch. That would be Part No. 54H on the carbonbrush.com site, except for the length, which is .125 inch shorter than the brushes I purchased. Their price is $3.28 each. And it appears you can buy two at a time instead of two dozen. I haven't done any business with the company (actually Arrowhead Electric Co.) but perhaps you or another adventurous tinkerer might want to give them a try.

I also found the commutator of my Bosch motor to have a big trough in it, so I chucked the armature shaft into an old 1/2-inch drill I bought at a dead farmer's auction awhile back and smoothed the commutator out with a flat file and some #600 paper (someone later told me the carbide or garnet or whatever abrasive leaves a residue that's hard on brushes, but I figured what's done is done).

If the commutator isn't too bad, I guess it's also possible to pry back the end tabs on the brush retainers and simply pop out the old and pop in the new. Solder in the new pigtails and you're all set.

Russ

Have taken the blower motor and fan out of a parts car and found the staked areas around the rim of the can which you filed to get the back cover off. On this type of fan motor, is the commutator and therefore brush set at this end of the motor or back under the fan? Want to clean and repair this one before doing anything to the one in the running car, as it is still working although a bit noisy.

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1961 190Db retired
1968 220D/8 325,000
1983 300D 164,150

pretty extensive selection there, except I wish there was more information. It's nice to see a thread like this with folks actually getting into the guts of stuff and fixing it with what you have. Good to know I'm not alone when I take a device apart and fix it, rather than just replace it like most guys do. Also, this is far (thankfully!) away from the all to common " I found a awwsum new plastic pre-cleaner for my faux-euroheadlights!!!!!" thread.

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'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.

The brushes are directly under the cover. Trick is to file just enough off so the cover comes free while leaving enough material for re-staking. The blower fan comes right off. Just the support the outer cage and gently tap the motor shaft out. Taking the cage off allows you to thoroughly clean and lube the front bearing.

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Bill Reimels
Now down to one:
1972 300SE 3.5 W109 (Euro delivery)

It would have been nice to find the correct brush but the fan seemed like it was failing so I needed to act fast. The brushes I put in seemed to have less copper content than the originals which means they are most likely softer. Based on what I learned from my R/C car racing days brushes with a higher copper load can handle higher current loads but at a cost to higher comm wear. This seems to tie in with the heavy scoring I saw on the comm. If I am sacrificing brush life and a little performance I think it's an OK tradeoff for longer comm life.

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Bill Reimels
Now down to one:
1972 300SE 3.5 W109 (Euro delivery)

Bill,

Thanks for the answer on the location of the comm. and brushes. Will certainly help guide my fan motor tear down and repair effort. Sure wish someone knew which of these motor styles was the Bosch and which was the Siemens. Would make it a lot easier to discuss what we are dealing with when the subject comes up again.

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1961 190Db retired
1968 220D/8 325,000
1983 300D 164,150

Lycoming, as I recall you had a Siemens motor unit you were thinking of swapping into your W123, correct? Did you ever give it a try?

Russ

Well, Russ, I am still not sure if it is a Siemens motor or not. Due to the cold weather we have experienced, swapping into the driver W123 has not happened yet. Once the weather moderated, have had to spend some time on non MB d(r)um(b) brakes, what a pain. 'Bout the time I am done with that, the weather will be back to c(o)ol(d) and will have to wait on the fan motor again. As I noted above, I really would like to have some resolution to the question of what does a Bosch look like and what does the Siemens look like. The one I have from the parts car has the staked over segments at the bottom end which is away from the fan end. The end plate here and motor case are totally closed with no visual openings whatsoever. As per 'billrei', the brushes are apparently at this end on this style motor. How does this style differ from the other type motor? And, which is which?

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1961 190Db retired
1968 220D/8 325,000
1983 300D 164,150

My Siemens blower motor unit had SIEMENS molded into the plastic end cap that holds the motor unit in the blower housing. The end cap is attached to the motor with two screws (vs. one for the Bosch unit) and the connector the wiring harness plugs into uses a screw (or screws) as a retainer vs. a metal clip for the Bosch unit.

In the other thread where we discussed this, someone noted that Mercedes used a variety of motors in the W123. I assume the Bosch motor was used the most, but I wouldn't be surprised if a third motor variety was lurking out there...BMW used a Sophica in their 5 series about the same time, so who knows?

The motor that Worldpac vendors such as Fastlane offers is the Bosch motor...so a picture of that one is readily available. Here's a link.
http://img.eautopartscatalog.com/live/R301027212BOS.JPG Note that the brushes/commutator are at the end opposite the fan. The brushes are at the fan end of the Siemens motor and inaccessible if you don't remove the fan from the armature shaft.

The Siemens motor has huge brushes, so brush wear and correspondingly commutator wear are drastically reduced over the Bosch motor. If you have a working Siemens motor in your car I'd see no need to keep a spare lying around.

BTW, I just swapped out the parking brake shoes in my '82 300td, so I had a refresher in drum brakes myself.

Russ M

I guess my motor is more like the Bosch unit but my motor is not open on the brush end like the motor pictured. On my motor the can went the full length. On some posts folks were talking about extending the life of their motors buy putting tinfoil between the spring arms and brush. My motor used long coil springs that would have supplied brush tension until the brush was completely gone. There was no name on either the black plastic housing or motor case. My housing however used the clip to hold the plug.

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Bill Reimels
Now down to one:
1972 300SE 3.5 W109 (Euro delivery)

Well the mystery for me is solved, I never expected to find the motor name on the plastic outer cover. Yeah, the one from the parts car is a Siemens, and the end cap is attached to the motor with two screws. If the weather isn't too bad tomorrow I will attempt a look at the one in the driver, but that means removing the knee shield once again.

However, there now appear to be at least three motors that were used in this service, Bosch, Siemens, and (???). Did the electrical fittings from all of these motors interchange? Also did the plastic housings at least interchangeably fit to the top housing part left in the car? May be a problem attaching the plastic housing to the various motors, as the Bosch uses one screw and Siemens uses two. Billrei maybe yours is just a revised Bosch unit, did it use one or two screws to the plastic housing?

Thanks Russ & Billrei and all who responded in these several threads about fan motors.

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1961 190Db retired
1968 220D/8 325,000
1983 300D 164,150

The blower motor in my 84 TD quit about two weeks ago. It was a siemens unit. (which I assuemed was a 'cheapie' replacement deal, guess I was wrong) I replaced it with the Bosch unit out of the parts car. I still have the dead one, can it be rebuilt??? I guess I can take it apart and find out. never taken apart a electric motor before... guess it is an opportunity to learn. Anything I should be careful/aware of .
Thanks
jason

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46 WDX Power Wagon

84 300TDT daily driver

My motor attached to the plastic housing with 2 screws.

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Bill Reimels
Now down to one:
1972 300SE 3.5 W109 (Euro delivery)

You'll have to drive the armature shaft off of the fan for starters. I used a drift and a heavy hammer to punch out the end of the shaft, supporting the fan with the open jaws of a bench vise. Once the fan is off, you can inspect the brushes.

The Siemens brushes are quite different from the ones on the Bosch motor, shaped like crescents vs. a straight bar. The brushes are mounted in kind of a cantilever manner and are spring-loaded to pivot against the commutator. They're actually mounted externally on the motor and look fairly easy to replace, but could be a challenge to find. You might check the sources I mentioned earlier in this thread.

Russ M