Westerbeke 9.0 BCG Technical Manual page 197

B. EXCITER ROTOR
1. Auxiliary windings 1.0 - 1.2 ohm. (Readings taken between each pair of windings: a + b, b + c, c +a.)
Winding connections can be left soldered at their connection points. If the readings are believed to be
incorrect, unsolder the connections and recheck for resistance readings.
2. Diodes (six diodes are mounted on the exciter rotor; they rectify the AC voltage produced by the three
groups of auxiliary windings to DC voltages and supply this DC voltage to the rotating field windings.)
Resistance Value
A resistance value through the diode
Infinite resistance blocking
• Resistance
------~I ~I~~
______
~------
Infinite - - - -
The diodes can be easily checked in place with the use of a common automotive 12-volt high beam
headlight bulb, some jumper leads and the generator's 12-volt starting battery. (See the next page.)
A short or an open in a diode can easily be found with the above without having to unsolder and isolate
each diode to check it with an ohmmeter.
NOTE: Attempting to check diodes in place with an ohmmeter will give erroneous readings
on the diodes due to the auxiliary windings connections.
Red & While
Exciter Rotor
191 Westerbeke Generators