Check Rotor Resistance Through The Brush Wires - Briggs & Stratton 040298 Service & Troubleshooting Manual

2
2
Figure 16
3. Measure the resistance and compare it to the
specifications listed in Section 4.
• A reading within the specifications listed is
acceptable.
• A reading of infinity or high resistance indicates
an opening in the excitation winding. Replace the
stator.
• A low reading indicates a shorted stator winding.
Replace the stator.
4. Connect one test lead to a stator power wire. Connect
the other test lead to one of the stator excitation
wires.
• A reading of infinity should be measured.
• A reading other that infinity indicates a power
winding shorted to an excitation winding.Replace
the stator.
5. Connect one test lead to an excitation wire. Connect
the other test lead to a proper metal ground.
• A reading of infinity should be measured.
• A reading other than infinity indicates a winding
shorted to ground. Replace the stator.
36

Check Rotor Resistance Through the Brush Wires

In an effort to eliminate the need to disassemble the engine/
alternator assembly, the rotor resistance can be measured
through the brush wires. This may, or may not provide
conclusive results. Resistance measured through the brush
wires will likely result in a slightly higher reading than the
specifications listed in Section 4. If a measurement is not
within 10% of specifications listed in Section 4, a rotor
amperage test must me performed. To check the rotor
resistance:
1. Set meter to measure Ohms.
2. Connect the test leads to the brush wires, red (#4)
and black (#1) (Figure 17) Previously diconnect from
voltge regulator.
Figure 17
3. Measure the rotor resistance. Compare it to the
nominal resistance from the specifications listed in
Section 4.
• A reading of infinity or a very high resistance
indicates an open circuit or a partially open
condition in the rotor windings. Before replacing
the rotor, proceed to Bypass the Automatic
Voltage Regulator.
• A very low resistance indicates a shorted rotor.
Replace the rotor.
• If resistance is within specifications, proceed to
Step 4.
4. Connect one test lead to a proper metal ground on
the engine or alternator and the other test lead to
either brush wire.
• A reading of infinity should be measured. if a
reading of infinity is measured rotor resistance is
within specifications, the rotor is functioning
properly.
• A reading other than infinity indicates a rotor
winding shorted to the rotor shaft. Replace the
rotor.