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Perform Resistance Measurement Of Coils Of Integrated Starter Alternator - AR15.40-P-0003-04MRT

Engine 256.9 

MODIFICATION NOTES

11.11.2020 Use a 4-way milliohm meter to prevent incorrect measurements.    
TEST SPECIFICATIONS OF INTEGRATED STARTER ALTERNATOR

Number Designation Engine 256.9
BE15.40-P-1002-06MRT Measurement of phase resistances Resistances of phases U-V, V-W, W-U 9, 1 ±0, 3
Resistances of phases X-Y, Y-Z, Z-X 8, 7 ±0, 3
For picture, see AR15.40-P-0003-04MRT 

IMPORTANT 18 coils are connected, in each case, in star arrangement in phases (U), (V), (W) and (X), (Y), (Z).

The phase resistance must be measured with a 4-way milliohm meter to prevent incorrect measurements.

  1. Perform 3 resistance measurements in phases (U) - (V), (V) - (W) and (W) - (U) and compare with specified value.
  2. Perform 3 resistance measurements in phases (X) - (Y), (Y) - (Z) and (Z) - (X) and compare with specified value.
    G14548275Courtesy of MERCEDES-BENZ USA

    IMPORTANT If a coil connection is damaged, the overall resistance will increase or decrease.

    If the measurement values lie outside the tolerance: Replace the integrated starter alternator.