Briggs & Stratton 86262GS, Familiarization & Troubleshooting Manual

Page: 83 / 128

To diagnose, use the “Rotor Current Draw Test.”
•• Step 2 Rotor Current Draw Test
• Locate the brush wires. (Normally these wires are #4
and #1.) Isolate the brushes from the bridge rectifier or
voltage regulator.
• Connect a (DC) Amp Meter between the positive
brush wire #4, and the positive post on a 12VDC
battery.
• Connect a jumper wire between the negative brush and
the negative post on the battery (See Figure 3.40).
• Start the engine and monitor amp draw.
It should not change while the unit is running or static.The
(DC) Amp draw will be determined by the specified
resistance of the rotor being tested.
To find the desired amp draw, use Ohms Law:
Voltage divided by amperage equals resistance.
For example: 12VDC divided by a rotor resistance of 24
ohms equals an amp draw of 0.5 amp.
NOTE:
Amp draw may vary slightly due to exact
battery voltage, rotor resistance, and meter
calibration etc. Look for extreme differences.
Analyze the test results as follows:
If the rotor current draw is higher than specified, a flying
short exists in the rotor.
If current draw is lower than specified, a flying open exists in
the rotor.
If current draw is within specifications, rotor is OK.
Test 8:
— Check Stator Excitation (DPE) Windings
NOTE:
The excitation wires may be colored or
numbered.The numbered wires are #2 and #6.The
colored wires are blue and red. Be sure not to
confuse the colored excitation wires with the
colored power wires.The excitation wires are the
wires connected to the power regulator board.
• Set the VOM to its “OHM” scale.
• Connect the test leads to the stator excitation wires
(Figure 3.41).
Measure the resistance and compare it to the nominal
resistance from the appropriate table (Briggs & Stratton
Power Products
®
“Portable Generator Rotor/Stator
Resistance Tables Pub. #87971 Rev 6 or later).
A reading of infinity or high resistance indicates an opening
in the excitation winding.
A low reading indicates a shorted stator winding.
81
Section 3 • Generator Diagnostics and Adjustments
Portable Generator Familiarization & Troubleshooting Guide
Replace Rotor
Replace Rotor
Replace Stator
Figure 3.41 — Checking DPE Resistance
Figure 3.40 — Rotor Current Draw Test