Bosch IF slip ring replacement

Replacing slip rings on internal fan (IF) Bosch alternators

Applications: BMW, Mercedes, Porsche, Saab, Volvo and other European and Domestic cars with Bosch internal fan alternators. Note, this article applies to those models with 7mm shaft which was used on many cars made during the 90's and early 2xxx models.

The original slip ring material is quite thin, only about 1mm thick so if the brushes have worn very far into the material it’s time to replace the slip rings. The job is not so difficult as it is a bit tricky. You will need a small bearing puller, a good soldering iron and an ohm meter along with the skills to use them.

Note the picture. These slip rings were removed from a Volvo 960 alternator.

1. To remove the slip rings you will need to dismantle the alternator and remove the rear bearing. With the ohm meter check the reading across the two slip rings and write it down. When finished with the job the reading should be the same.

2. Unsolder the wires from the tabs at the base of the slip ring assembly. If you don’t have a suitable puller for the slip rings they can be hack sawed most of the way through and split so they will come off. It’s VERY IMPORTANT that all of the slip ring material is removed. If even a chip is left of the insulation material from the old slip ring the new one won’t seat properly.


3. NOTE: The new slip ring must be installed so the little knob on the slip ring goes into the notch that you can see in the fan that is spot welded to the rotor. Study the picture.
(If the slip rings were installed backwards the current would be flowing backwards through the rotor windings. Not good)



5. You will need a tool to press the slip ring on. Note the picture shows a tool made from ¾” plastic pipe with a cap glued to it. Cut a piece of the plastic pipe about 40.75mm. Use a cap that is flat across on the inside and cement it on.

Make sure this tool drives the end of the slip ring assembly as well as the base of the slip ring so the plastic slip ring assembly doesn’t break. Spend a few minute be sure you have it right.

It won’t take much to press the new slip ring assembly in place. BE SURE the copper tips of the wires aren’t under the new slip ring assembly. When properly installed the outer end of the slip ring assembly will be about 4.50mm past the end of the rotor shaft.



6. Use good solder to solder the wires. Note the replacement slip ring assembly has small holes in the tab so you can insert the wires and then solder them for an excellent job.

7. Press the new rear bearing in place and reassemble the alternator.

Click here to purchase Bosch internal fan slip ring and parts

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Below are the Bosch alternator numbers that use the above slip rings:

0120335006 0120335007 0120335008 0120335010 0120335011 0120335012 0120465003 0120465004 0120465006 0120465007 0120465008 0120465009 0120465010 0120465011 0120465012 0120465013 0120465014 0120465015 0120465016 0120465017 0120465018 0120465020 0120465021 0120465023 0120465026 0120465027 0120465028 0120465029 0120465031 0120485005 0120485006 0120485007 0120485008 0120485011 0120485012 0120485015 0120485017 0120485018 0120485020 0120485022 0120485023 0120485024 0120485025 0120485026 0120485028 0120485029 0120485030 0120485032 0120485034 0120485036 0120485038 0120485039 0120485041 0120485043 0120485044 0120485046 0120485047 0120485048 0120485050 0123100001 0123100002 0123100003 0123105001 0123105002 0123110004 0123110005 0123110006 0123110007 0123110008 0123114005 0123115009 0123115010 0123115011 0123115012 0123115013 0123115014 0123120001 0123212001 0123213005 0123213006 0123213007 0123214002 0123215001 0123310001 0123310002 0123310003 0123310004 0123310005 0123310006 0123310007 0123310008 0123310010 0123310011 0123310012 0123310013 0123310014 0123310015 0123310016 0123310017 0123310018 0123310019 0123310020 0123310022 0123310023 0123310024 0123310025 0123310026 0123310027 0123310028 0123310029 0123310030 0123310031 0123310032 0123310033 0123310034 0123310035 0123310037 0123310038 0123310039 0123310040 0123310041 0123310042 0123310043 0123310044 0123310046 0123310047 0123315001 0123315002 0123315003 0123315004 0123315005 0123315006 0123315007 0123315008 0123315013 0123315015 0123315016 0123315017 0123315018 0123315019 0123315020 0123315021 0123315022 0123315500 0123315501 0123315502 0123315503 0123320001 0123320002 0123320003 0123320004 0123320005 0123320006 0123320007 0123320008 0123320009 0123320010 0123320011 0123320012 0123320014 0123320016 0123320017 0123320018 0123320019 0123320020 0123320021 0123320022 0123320023 0123320024 0123320025 0123320026 0123320027 0123320028 0123320029 0123320030 0123320031 0123320032 0123320033 0123320034 0123320035 0123320036 0123320037 0123320038 0123320039 0123320040 0123320041 0123320042 0123320043 0123320044 0123320045 0123320046 0123320047 0123320048 0123320049 0123320050 0123320051 0123320052 0123320053 0123320054 0123320055 0123320057 0123320058 0123320059 0123320060 0123320061 0123320062 0123325002 0123325003 0123325004 0123325005 0123325006 0123325007 0123325008 0123325010 0123325011 0123325012 0123325013 0123335001 0123335002 0123335003 0123335004 0123335005 0123335006 0123335008 0123340001 0123340002 0123340003 0123340005 0123340006 0123340007 0123345004 0123500001 0123500002 0123500004 0123500005 0123500006 0123500007 0123500008 0123500009 0123505001 0123505002 0123505003 0123505004 0123505005 0123505007 0123505008 0123505009 0123505010 0123505011 0123505012 0123505013 0123505014 0123505015 0123505016 0123505017 0123505018 0123510001 0123510002 0123510003 0123510004 0123510005 0123510006 0123510007 0123510008 0123510009 0123510010 0123510011 0123510012 0123510013 0123510014 0123510015 0123510016 0123510017 0123510018 0123510020 0123510021 0123510022 0123510023 0123510026 0123510027 0123510028 0123510029 0123510030 0123510031 0123510032 0123510033 0123510034 0123510037 0123510038 0123510039 0123510040 0123510041 0123510042 0123510043 0123510044 0123510045 0123510046 0123510047 0123510048 0123510049 0123510050 0123510051 0123510052 0123510053 0123510054 0123510056 0123510057 0123510058 0123510059 0123510060 0123510061 0123510062 0123510063 0123510064 0123510065 0123510066 0123510067 0123510068 0123510069 0123510070 0123510071 0123510072 0123510073 0123510074 0123510075 0123510079 0123510080 0123510081 0123510082 0123510088 0123510089 0123510091 0123510092 0123510093 0123510094 0123510095 0123510096 0123510099 0123510100 0123510101 0123510102 0123512500 0123512501 0123515002 0123515003 0123515004 0123515007 0123515008 0123515009 0123515010 0123515011 0123515012 0123515013 0123515014 0123515016 0123515017 0123515018 0123515020 0123515021 0123515022 0123515023 0123515024 0123515025 0123515028 0123520002 0123520003 0123520004 0123520005 0123520006 0123520007 0123520008 0123520010 0123520011 0123520012 0123520013 0123520014 0123520017 0123520500 0123525001 0123525500 0123525503 0123540001 0123540002 0123540003 0123540004 0123545001 0123545002 0123545003 0123545004 0124625019