Testing For A Shorted No72'Le; Troubleshooting - Sears Craftsman 934.20105 Owner's Manual

MAINTENANCE AND TROUBLESHOOTING Page 27
2. The CONTACT TIP's purpose is to transfer
welding current to the welding wire while allow-
ing the wire to pass through it smoothly.
a. Always use a contact tip stamped with the
same diameter as the wire it will be used
with.
b_
If the wire burns back into the tip, remove the
tip from the gun and clean the hole running
through itwith an oxygen-acetylene torch tip
cleaner. This is especially important to do
after an aluminum wire burn-back.
C,
Over time, the hole in the contact tip will
become worn by the wire passing through it.
The more worn this hole becomes, the less
efficient is the transfer of welding current to
the wire and eventually arc breakage and
difficult arc starting will result. Replace con-
tact tips when signs of wear become appar-
ent.
3. The NOZZLE prevents the electrically"hot" con-
tact tip from contacting the work piece.
KEEP THE NOZZLE CLEAN! During the welding
process, spatter and slag will build up inside the
nozzle and must be cleaned out periodically.
a. Always coat the inside of a new or freshly
cleaned nozzle with anti-stick spray or gel.
b. Stop welding and clean any accumulated
slag or spatter from the nozzle every 5 to 10
minutes of welding time.
C*
When welding overhead, if any molten metal
drips from the weld puddle and falls into the
nozzle, STOP WELDING IMMEDIATELY
and clean the nozzle.
d. If the slag cannot be thoroughly cleaned
from the nozzle, REPLACE THE NOZZLE!
Failure to keep the nozzle adequately cleaned can
result in a SHORTED NOZZLE which results when
spatter build-up bridges the insulation in the nozzle
allowing welding current to flow through it as well
as the contact tip. When shorted, a nozzle will
steal welding current from the wire whenever it
contacts the grounded work piece. This causes
erratic welds and reduced penetration. In addition,
a shorted nozzle overheats the end of the gun
which can DAMAGE the gas diffuser and/or con-
ductor tube.
TESTING FOR A SHORTED NOZZLE
Arcing between the nozzle and the work piece
ALWAYS means the nozzle is shorted, but this can
be hard to detect through the lens of a welding
helmet. The following testing method is another
way to tell if a nozzle is shorted.
With the welder unplugged from the AC power
source, touch the probes of an ohmmeter or conti-
nuity tester to the end of the contact tip and the
outside of the nozzle. If there is any continuity at
all, the nozzle IS shorted. Clean or replace as
needed.
TROUBLESHOOTING
The following TROUBLESHOOTING section is
provided as a guide to help resolve some of the
more common problems that could be encoun-
tered. Should you or qualified repair personnel be
unable to resolve a problem or determine which of
the possible solutions will remedy a specific prob-
lem, contact MIG WELDER SERVICE for over-
the-phone diagnostic assistance at:
(800)-328-2921. In Minnesota call: (612) 884-
3211.
BEFORE CALLING MIG WELDER SERVICE,
have the welder unplugged from the AC power
source, the side panels removed, and the tele-
phone as near to the welder as possible.
ELECTRIC SHOCK CAN KILL!
_ARC RAYS CAN INJURE EYES AND
BURN SKIN!
FIRE OR EXPLOSION CAN CAUSE
DEATH, INJURY, AND PROPERTY DAMAGE!
FUMES, GASSES, AND VAPORS CAN
CAUSE DISCOMFORT, ILLNESS, AND DEATH!