Mercedes Benz Alternator Parts Replacement

Mercedes Benz Alternator Parts Replacement


Alternators & Regulators Bosch with internal regulators
Alternators manufactured by Bosch are regular 3-phase, self-rectifying variety alternators.

Bosch 75 by 55-amp alternators use3 detrimental 3 optimistic and diodes connected to stator windings to rectify recent, Bosch 90 and 80-amp alternators use 14 diodes.

All alternators use 3 exciter diodes linked to stator windings, though the motor is jogging these diodes switch off the alternator indicator gentle and supply electrical power to the voltage regulator, Bosch regulators are transistorized good condition and integral with alternator.

ALTERNATOR Application
Product Volts/Amps

(1) Manufacturer’s Component No.

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

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

1. You can hook up a voltmeter to the alternator “B+” terminal and floor, voltmeter ought to point out battery voltage, if not test wiring concerning battery and alternator.

2. Convert ignition on and check out that alternator indicator light-weight comes on, if mild does not appear on, check out wiring concerning warning mild and alternator, which include indicator bulb.

1. Assure connections at battery, alternator, and starter are clean up and tight, guarantee alternator engine and entire body are properly grounded, be certain alternator belt is limited and in excellent ailment.

2. Join ammeter following manufacturer’s guidelines, hook up voltmeter qualified prospects to battery terminals.

3. Start out engine and run at 3000 R.P.M. alter carbon pile to get maximum alternator output, do not allow voltage to go down below 12.6 volts.

4. Alternator output must equal alternator rated output, minus 16-20 amps, if reading is 16-20 amps down below alternator ranking, switch regulator and retest, if output is continue to much too small, restore or swap the alternator.


1. Connect ammeter subsequent manufacturer’s guidance, join voltmeter prospects to battery terminals, run engine at 3000 R.P.M.

2. Operate engine right up until voltage stops mounting, voltage ought to be 13.5-14.5 volts, if examining is incorrect, remove regulator and make certain brushes are longer than 6 m.m..

3. If brushes are ok and regulator fails to preserve voltage within just specified limitations, exchange regulator and retest, if voltage is nevertheless incorrect, maintenance or swap alternator.


1. Get rid of nut, lock washer, and pulley, bear in mind position of spacers, Then take away lover assembly and important, scribe mark on entrance and rear housings, get rid of voltage regulator and take away screws, individual entrance and rear housings.

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

Remove stator assembly.
3. Unsolder stator from diode assembly take out bearing wave washer or o ring from rear of housing.

3. Assistance front housing and cautiously press out rotor, do not let rotor to tumble, eliminate screws securing bearing retainer, take out retainer front bearing and seal clear away rear bearing from slip ring at conclusion of rotor.

Screening & Mend
Diode Assembly
1. Position ohmmeter scale on x100 scale link ohmmeter leads throughout “B+” terminal and 3 stator terminals a person at a time, reverse potential customers, ohmmeter ought to indicate continuity in 1 route only.

2. Reconnect ohmmeter leads across negative and 3 stator terminals a single at a time.

Reverse leads ohmmeter need to show continuity in one way only.

3. Join ohmmeter potential customers across “D+” terminal and 3 stator terminals a person at a time.

Reverse sales opportunities, ohmmeter ought to reveal continuity in a person path only, if diodes are found to be defective, replace the diode assembly.

Fig. 3: Diode Assembly Check Diode assembly for 55 amp alternator is revealed, other people are comparable.

1. Put ohmmeter on lowest scale, link ohmmeter across stator qualified prospects, resistance between potential customers really should be 14 15 ohms for 55-amp alternator and .09 10 ohms for 65 by 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. Hook up ohmmeter amongst stator core and stator direct, no continuity really should exist, if continuity exists, stator is grounded and have to be changed.

1. Location ohmmeter on most affordable scale, link ohmmeter across slip rings, resistance should be 3 4-3.75 ohms for 55 amp alternator and 2.8 3.1 ohms for 65 by 90 amp alternators.

2. If resistance is too low, rotor has brief circuit and it ought to be replaced if resistance is infinity no continuity, rotor has open up circuit and ought to be replaced.
3. Area ohmmeter on x1000 scale, reconnect ohmmeter amongst either the slip ring and rotor core, no continuity ought to exist, if continuity exists, rotor is grounded and must be replaced.

4. Clean up slip rings making use of a really high-quality sandpaper, rings which are worn or pitted really should be turned on lathe, least ring diameter is 1 1/16″ 26.8 m.m. if slip rings are outside of fix, exchange slip rings as outlined in actions 5 and 6.
5. Take out rear bearing from slip ring stop of rotor, unsolder wires from slip rings and bend up finishes of rotor winding, pull off slip rings, assure ends of rotor winding are not harmed.

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

The Bearings
Generally substitute bearings, if alternative front bearing is sealed on 1 side only, open up facet must experience rotor, if substitute rear bearing is sealed on one aspect only, open side need to experience absent from rotor.

Guarantee brushes are extended than 6 m.m. swap if necessary, unsolder brushes from voltage regulator, solder new brushes, and do not permit solder to operate into strands of brush potential customers.

Brush ought to be absolutely free to slide in holder with normal spring stress of 10-14.

1. Put in the bearing, retainer, and screws in entrance housing, press rotor onto housing.

Press bearing on slip ring end of the rotor, solder stator to diode assembly, exercise treatment when soldering close to diodes due to achievable heat problems.

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

3. Set up key, fan assembly, and spacers, put in the pulley, lock washer and nut, tighten nut to 23-29 ft. 3-4 Nm. Make certain rotor spins freely, and set up voltage regulator and capacitor.