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

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)

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.

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

Bill -- it occurred to me that you never got an answer to this question. There is a blower control amp behind the glove box. Go to your favorite Worldpac vendor's site and click "blower regulator" in the climate control section. That's what you're dealing with.


Russ

Thanks Russ, Yipes! Remanufactured it's $162!! I hope it is OK or that it can be rebuilt with Radio Shack parts....

I have the type 2 ACC system with a new aluminum body servo. The system seems to work OK except when in Auto HI the fan never goes into full highspeed like it does in Defrost mode. Is this normal?

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

Not sure, Bill. I don't have any experience with the servos and frankly, plan to stay away from any cars so equipped. I see that Performance products has a solid-state control system to replace the servo completely...only $600!

I will say that the fans on my W123s will blow at high speed in all modes.

Since you seem to be drawing a blank in this thread, maybe you want to start a new one under a different title. Did you see the thread on this Bentley forum?
http://tech.bentleypublishers.com/category.jspa?categoryName=mercedes-benz

Hmm....I wasn't aware Bentley even published manuals for Mercedes, let alone the W123.

Russ