Mercedes Benz Alternator Parts Replacement

Mercedes Benz Alternator Parts Replacement


Alternators & Regulators Bosch with inner regulators
Alternators built by Bosch are conventional 3-phase, self-rectifying form alternators.

Bosch 75 by 55-amp alternators use3 negative 3 favourable and diodes related to stator windings to rectify present-day, Bosch 90 and 80-amp alternators use 14 diodes.

All alternators use 3 exciter diodes linked to stator windings, even though the engine is working these diodes transform off the alternator indicator light and provide electrical power to the voltage regulator, Bosch regulators are transistorized solid condition and integral with alternator.

ALTERNATOR Application
Model Volts/Amps

(1) Manufacturer’s Section No.

190E 14/70 489 928
190D 14/70 489 897

All Many others 14/70 N/A
(1) Bosch alternator portion figures are preceded by the numbers 120 or beginning with an AL lettering a quantity and ending with an X.

1. You can connect a voltmeter to the alternator “B+” terminal and floor, voltmeter should really indicate battery voltage, if not check out wiring between battery and alternator.

2. Flip ignition on and check out that alternator indicator mild will come on, if mild does not occur on, check wiring concerning warning gentle and alternator, which include indicator bulb.

1. Guarantee connections at battery, alternator, and starter are clean and tight, guarantee alternator engine and entire body are effectively grounded, ensure alternator belt is tight and in great ailment.

2. Link ammeter following manufacturer’s recommendations, join voltmeter potential customers to battery terminals.

3. Start off engine and run at 3000 R.P.M. regulate carbon pile to acquire highest alternator output, do not permit voltage to go below 12.6 volts.

4. Alternator output really should equal alternator rated output, minus 16-20 amps, if reading through is 16-20 amps beneath alternator rating, switch regulator and retest, if output is however also reduced, maintenance or replace the alternator.


1. Join ammeter pursuing manufacturer’s guidelines, hook up voltmeter qualified prospects to battery terminals, run motor at 3000 R.P.M.

2. Operate motor until voltage stops mounting, voltage must be 13.5-14.5 volts, if reading through is incorrect, take away regulator and guarantee brushes are for a longer time than 6 m.m..

3. If brushes are alright and regulator fails to retain voltage in specified restrictions, replace regulator and retest, if voltage is continue to incorrect, fix or switch alternator.


1. Get rid of nut, lock washer, and pulley, remember posture of spacers, Then eliminate admirer assembly and key, scribe mark on front and rear housings, get rid of voltage regulator and remove screws, independent front and rear housings.

2. Disconnect capacitor from terminal take away nut, insulators, screws and washers.

Take out stator assembly.
3. Unsolder stator from diode assembly get rid of bearing wave washer or o ring from rear of housing.

3. Aid entrance housing and carefully push out rotor, do not enable rotor to slide, remove screws securing bearing retainer, eliminate retainer entrance bearing and seal remove rear bearing from slip ring at conclude of rotor.

Screening & Repair
Diode Assembly
1. Spot ohmmeter scale on x100 scale connect ohmmeter qualified prospects across “B+” terminal and 3 stator terminals one at a time, reverse potential customers, ohmmeter really should indicate continuity in just one course only.

2. Reconnect ohmmeter potential customers throughout adverse and 3 stator terminals just one at a time.

Reverse qualified prospects ohmmeter should show continuity in a person direction only.

3. Link ohmmeter sales opportunities throughout “D+” terminal and 3 stator terminals a single at a time.

Reverse prospects, ohmmeter should really indicate continuity in one particular direction only, if diodes are observed to be defective, switch the diode assembly.

Fig. 3: Diode Assembly Exam Diode assembly for 55 amp alternator is demonstrated, other folks are identical.

1. Spot ohmmeter on lowest scale, hook up ohmmeter throughout stator qualified prospects, resistance among qualified prospects ought to be 14 15 ohms for 55-amp alternator and .09 10 ohms for 65 through 90 amp alternators, if resistance is incorrect, stator has open up or shorted windings and will have to be changed.

2. Put ohmmeter on X 1000 scale. Join ohmmeter involving stator main and stator lead, no continuity should exist, if continuity exists, stator is grounded and should be replaced.

1. Position ohmmeter on cheapest scale, connect ohmmeter across slip rings, resistance should really be 3 4-3.75 ohms for 55 amp alternator and 2.8 3.1 ohms for 65 as a result of 90 amp alternators.

2. If resistance is also small, rotor has short circuit and it ought to be changed if resistance is infinity no continuity, rotor has open up circuit and will have to be changed.
3. Spot ohmmeter on x1000 scale, reconnect ohmmeter amongst both the slip ring and rotor main, no continuity really should exist, if continuity exists, rotor is grounded and need to be replaced.

4. Thoroughly clean slip rings applying a pretty wonderful sandpaper, rings which are worn or pitted should really be turned on lathe, minimum ring diameter is 1 1/16″ 26.8 m.m. if slip rings are outside of mend, exchange slip rings as outlined in techniques 5 and 6.
5. Take out rear bearing from slip ring conclude of rotor, unsolder wires from slip rings and bend up finishes of rotor winding, pull off slip rings, make certain ends of rotor winding are not ruined.

6. Insert the ends of rotor winding into slip ring and push new slip ring on to rotor, slip ring stop must be 9/64″ 3.5 m.m. from finish of the collar, solder rotor winding to slip ring terminals, convert rings on lathe and retest rotor, greatest slip ring run out is 0012″.03 m.m..

The Bearings
Always replace bearings, if substitute front bearing is sealed on one aspect only, open facet should facial area rotor, if substitute rear bearing is sealed on one particular side only, open side will have to experience away from rotor.

Guarantee brushes are for a longer period than 6 m.m. replace if needed, unsolder brushes from voltage regulator, solder new brushes, and do not allow solder to operate into strands of brush qualified prospects.

Brush must be absolutely free to slide in holder with ordinary spring rigidity of 10-14.

1. Set up the bearing, retainer, and screws in front housing, push rotor onto housing.

Push bearing on slip ring close of the rotor, solder stator to diode assembly, exercise care when soldering around diodes due to feasible warmth harm.

2. Install insulators on stator assembly, assemble stator assembly and rear housing, set up wave washer or O ring in rear housing, align the scribe marks and assemble front and rear housings.

3. Put in crucial, admirer assembly, and spacers, put in the pulley, lock washer and nut, tighten nut to 23-29 ft. 3-4 Nm. Be certain rotor spins freely, and install voltage regulator and capacitor.