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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.
