1
Low control voltage
CheckMeasure coil voltage while attempting pull-in. Must be ≥85% of rated.
FixCheck transformer sizing, control wiring length, dropping resistors.
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2
Pitted / welded tips
CheckVisual; measure mV drop across closed tips at load current.
FixReplace tips or contactor.
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3
Undersized contactor for FLA
CheckVerify NEMA/IEC rating ≥ motor FLA × duty factor.
FixUpsize.
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4
Loose terminations causing arcing
highCheckIR camera under load; torque check at rest.
FixRe-torque to spec (typ. 20–35 in-lb for #10–#6 wire).
ToolsIR thermometer or thermal camera · Torque screwdriver
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5
Coil shorted turn
CheckResistance comparison to spec; hum tone changes.
FixReplace coil or contactor.
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Safety
Lockout/tagout before opening enclosures. Verify zero energy. Bleed system pressure before opening any pneumatic connection.