Shunt Field Coil Resistance And Ground Test Procedure - Lincoln Electric SAE-300 HE Service Manual

LINCOLN ELECTRIC

SHUNT FIELD COIL RESISTANCE AND GROUND TEST PROCEDURE

Service and repair should be performed by only Lincoln Electric factory trained personnel. Unauthorized
repairs performed on this equipment may result in danger to the technician or machine operator and will
invalidate your factory warranty. For your safety and to avoid electrical shock, please observe all safety
notes and precautions detailed throughout this manual. If for any reason you do not understand the test
procedures or are unable to perform the test/repairs safely, contact the Lincoln Electric Service Department
for electrical troubleshooting assistance before you proceed. Call 1-888-935-3877.
TEST DESCRIPTION
This procedure will determine if the Welding Generator Shunt Field Coils are open, shorted or grounded
IMPORTANT: The machine should be clean and windings must be completely dry before this test is done.
MATERIALS NEEDED
Volt/Ohmmeter
Wiring Diagram
TEST PROCEDURE
1. Turn off the engine on the SAE-300 HE machine.
2. Open one of the side doors and secure it with the hook provided.
3. Locate the brown and blue wires in the lead bundle exiting at the top of the welding generator
frame and disconnect them. See Wiring Diagram.
4. Using a volt/ohmmeter, measure the resistance between the brown and blue wires that connect the
shunt coils inside the generator frame. See Wiring Diagram. The resistance should measure about
50 to 54 Ohms* at 77° F (25° C).
5. If the resistance reading is correct, proceed to the Shunt Coil Ground Test.
6. If the resistance is significantly higher or lower than specified, examine the leads connecting the
shunt coils and the jumper lead connecting the two coils together. If the leads and connections are
undamaged, the shunt coils should be replaced.
Shunt Coil Ground Test:
7. Using a volt/ohmmeter, measure the resistance between either the brown or blue wires and a good
clean chassis ground. See Wiring Diagram. The resistance should be very high. 500,000 (500k)
Ohms minimum.
8. If the resistance is low, check the lead wires connected to the shunt coils and the jumper lead wire
connecting the two coils together. If these leads are in good condition and the low resistance is
determined to be defective coil. The shunt coils should be replaced.
9. Reconnect the wires and replace any covers that have been removed.
*NOTE: The resistance of the copper windings will change with temperature. Higher temperatures
will produce slightly higher resistance and lower temperatures will produce slightly lower resistance.
SAE-300® HE Service Manual
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