I recently experienced for the first time the blower motor blowing fuse no. 8 when the motor is on high. After much searching for a replacement new motor (I'm in it for the long haul with this car, and I wanted a permanent fix for about $100), I realize that they are simply unavailable at reasonable cost. I couldn't find a new bosch motor alone for my car...only the complete blower unit for over $400! So I found a used motor from a salvage yard for only $25, and decided to replace brushes in both (using one as a backup).

After much searching in this forum, and looking in small parts trays in Ace Hardware, I found a post by UtahPete in this forum identifying www.carbonbrush.com, as a good source for Bosch motor brushes. I bought the K44 brushes, 8 mm x 8 mm x 19 mm long for $5.35 ea. , plus reasonable shipping fee (about $6 and change) I placed the order on Wednesday last week, and on Saturday my parts arrived at home by U.S. Postal. Very good service, good product, perfect drop-in replacement.

The brushes are the exact size, but requiring sanding the contact end to proper angle and curve (I got it close, not too fussy).

It looks like there are three wear points on these motors...

1) Brushes...easily replaced with limited soldering & mechanical skills. I surmise that worn brushes cause an increase in current draw of the motor, causing fuse to blow.
2) Bearings....can't do much about these except to put a few drops of ATF and hope they will last as long as needed. I don't think they are replaceable.
3) Commutator...where the brushes contact the commutator, I observed about 1/16" of wear into the copper commutator on the two motors I have. I don't know how much life is left in the motor with this type of wear, or how much more wear the motor can take.

In the end, I just figured I would replace brushes, lubricate the bearing with ATF, and hope for the best. After brush replacement, the motor no longer blows the fuse. So I hope with brushes replaced in my two blower motors, that these will last for another 100,000 miles (?!?!?!).

I also see the fuse replacement option consisting of the fuse holder and wire allowing you to bypass the fuse in the fuse block (fuse no. 8 is a blue 25 amp), and replacing stock fuse with a 30 amp fuse....hardly seems worth the effort, for such a marginal increase.

Thanks to www.carbonbrush.com and UtahPete,

Mark

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1984 300TD Wagon, 407,800 mi (current daily driver)
1985 300DT Sedan, 330,000 mi (gone to that great autobahn in the sky)