Miller S-74 MPa Plus Owner's Manual - Page 40
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9-3.
Troubleshooting
Disconnect power before troubleshooting.
Trouble
Pressing gun trigger does not ener-
gize feeder. Shielding gas does not
flow and wire feeder does not feed.
Wire feeds, shielding gas flows, but
welding wire is not energized.
Wire feeds erratically.
Arc varies and welding wire is kinked
when feeding out gun.
No weld output; gun/feeder does not
work.
Erratic weld output.
Wire does not feed; burnback in con-
tact tip.
Gun overheating (water-cooled
models).
Motor does not run.
OM-289404 Page 34
Secure plug from gun control cable into Gun Control receptacle.
Have nearest Factory Authorized Service Agent check optional water flow switch, if applicable.
Check to see if ground clamp or weld cable is connected.
Verify proper wire size is selected (see Section 8-2).
Check drive roll pressure in wire feeder and gun.
Clean or replace drive rolls as necessary.
Check and replace liner if necessary.
Verify proper wire size is selected (see Section 8-2).
Check gun control cable connection.
Tighten and clean all connections.
Replace contact tip.
Verify proper wire size is selected (see Section 8-2).
Check drive roll pressure in wire feeder and gun.
Check and replace liner if necessary.
When welding aluminum, it is important to use minimal drive roll pressure and minimal brake tension
to achieve consistent wire feeding.
Verify drive roll size is correct.
Check drive roll pressure in wire feeder and gun.
Check and replace liner if necessary.
Be sure coolant flow rate is at least 1 qt/min.
Corrosion buildup in gun decreasing coolant flow rate. Backflush coolant system, clean coolant sys-
tem filter, and clean fittings.
Check drive roll pressure in wire feeder and gun.
Check and replace liner if necessary.
Have Factory Authorized Service Agent check feeder.
Remedy