Forney 125 FC Operating Manual page 23

A shorted nozzle results when spatter buildup 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 front-end of the gun.
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 continuity
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.
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