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Motor Trouble Guide
The purpose of this guide is to suggest common answers to electrical problems. The
information is not all-inclusive and does not necessarily apply in all cases. When unusual
operating conditions, repetitive failures, or other problems occur, consult an electric motor
service firm for assistance.
Trouble
Cause
–
What To Do
Motor fails to start.
Blown fuses – Replace with time-delay fuses
or circuit breakers. Check for grounded
winding.
Low voltage – Use higher voltage tap on
transformer terminals, increase wire size.
Check for poor connections.
Improper line connections – Check
connections against diagram supplied with
motor.
Overload tripped – Check and reset relay in
starter. Check heater rating against motor
nameplate current rating. Check motor load.
If the motor has manual re-set thermal
protector, check if it has been tripped.
Motor may be overloaded – Reduce load.
Increase motor size.
If permanent split capacitor motor, capacitor
may be open – Indicated by humming sound.
Replace run capacitor. See nameplate for
correct value.
Defective motor or starter – Repair or
replace.
Motor stalls.
Overloaded motor – Reduce load or increase
motor size.
Low motor voltage – See that nameplate
voltage is maintained.
Motor does not come up to speed.
Not applied properly – Consult motor service
firm for proper type. Use larger motor.
Motor takes too long to accelerate.
Excess loading; high inertia load – Reduce
load. Increase motor size.
Inadequate wiring – Increase wire size.
Check for poor connections.
Applied voltage too low – Reconnect to a
higher transformer tap. Increase wire size.
Check for poor connections.
Defective motor – Repair or replace.
Inadequate starting torque – Replace with
higher horsepower motor.
