Troubleshooting - Miller AC 251 Stick Owner's Manual

4-2. Troubleshooting

Trouble
No weld output; unit completely inop-
erative.
No weld output; fan motor FM running
and pilot light on.
Low weld output with no control.
Limited output and low open-circuit
voltage.
Erratic or improper weld output.
Fan motor FM does not run.
OM-194 414 Page 8
Be sure Power switch is On (see Section 3-1).
Be sure line disconnect switch is On (see Section 2-7).
Check line fuse(s) and replace if necessary (see Sections 2-7).
Check for proper input power connections (see Sections 2-6 and/or 2-7).
Thermostat(s) open (overheating). Allow fan to run; thermostat(s) closes when unit has cooled (see
Section 2-2).
Check position of Welding Current Control (see Section 3-1).
Check incoming power for correct voltage. Replace line fuse if open (see Section 2-7).
Check for proper input and output connections (see Sections 2-5 and/or 2-7).
Tighten all welding cable connections (see Sections 2-5).
Check for proper size and type of cable (see Section 2-5).
Check for proper input and output connections (see Sections 2-5 and/or 2-7).
Replace electrode.
Check and clear blocked fan blade; be sure blade is secure on shaft.
Have Factory Authorized Service Agent check fan motor FM.
Remedy