1. Disconnect power to the motor before performing service or maintenance.
2. Discharge all capacitors before servicing motor.
3. Always keep hands and clothing away from moving parts.
4. Be sure required safety guards are in place before starting equipment.
Problem
Likely Causes
What To Do
•
Motor is miswired.
•
Motor had been running,
then fails to start.
•
Fuse or circuit breaker tripped.
•
Stator is shorted or went to ground.
Motor will make a humming noise and
the circuit breaker or fuse will trip.
•
Disassemble motor and inspect windings and
internal connections. A blown stator will show a
burn mark. Motor must be replaced or the stator
rewound.
•
Motor overloaded or load jammed.
•
Inspect to see that the load is free. Verify
amp draw of motor versus nameplate rating.
•
Capacitor (on shingle phase motor)
may have failed.
•
First discharge capacitor. To check capacitor, set
volt-ohm meter to RX100 scale and touch its probes
to capacitor terminals. If capacitor is OK, needle will
jump to zero ohms, and drift back to high. Steady
zero ohms indicates a short circuit; steady high
ohms indicates an open circuit.
•
Motor fails to start
upon initial installation.
•
Starting switch has failed.
•
Voltage drop.
•
Disassemble motor and inspect both the centrifugal
and stationary switches. The weights of the
centrifugal switch should move in and out freely.
Make sure that the switch is not loose on the shaft.
Inspect contacts and connections on the stationary
switch. Replace switch if the contacts are burned or
pitted.
•
Motor runs but dies
down.
•
If voltage is less than 10% of the motor’s rating
contact power company or check if some other
equipment is taking power away from the motor.
•
Load increased.
•
Verify the load has not changed. Verify equipment
hasn’t got tighter. If fan application verify the air
flow hasn’t changed.
•
Motor takes too long
to accelerate.
•
Defective capacitor.
•
Test capacitor per previous instructions.
•
Faulty stationary switch.
•
Inspect switch contacts and connections. Verify that
switch reeds have some spring in them.
•
Bad bearings.
•
Noisy or rough feeling bearings should be replaced.
•
Voltage too low.
•
Make sure that the voltage is within 10% of the
motor’s nameplate rating. If not, contact power
company or check if some other equipment is taking
power away from the motor.
•
Motor runs in the
wrong rotation.
•
Incorrect wiring.
•
Rewire motor according to wiring schematic
provided.
•
Motor overload
protector continually
trips.
•
Load too high.
•
Verify that the load is not jammed. If motor is a
replacement, verify that the rating is the same as
the old motor. If previous motor was a special
design, a stock motor may not be able to duplicate
the performance. Remove the load from the motor
and inspect the amp draw of the motor unloaded. It
should be less than the full load rating stamped on
the nameplate.
•
Ambient temperature too high.
•
Verify that the motor is getting enough air for
proper cooling. Most motors are designed to run in
an ambient temperature of less than 40° C. (Note:
A properly operating motor may be hot to the
touch.)
•
Protector may be defective.
•
Replace the motor’s protector with a new one of
the same rating.
•
Winding shorted or grounded.
•
Inspect stator for defects, or loose or cut wires
that may cause it to go to ground.
•
Motor vibrates.
•
Motor misaligned to load.
•
Realign load.
•
Load out of balance. (Direct drive
application).
•
Remove motor from load and inspect motor by
itself. Verify that motor shaft is not bent. Rule of
thumb is .001” runout per every inch of shaft
length.
•
Motor bearings defective.
•
Test motor by itself. If bearings are bad,you will
hear noise or feel roughness. Replace bearings.
Add oil if the bearing is a sleeve bearing type or
replace bearings. Add grease if bearings have
grease fittings.
•
Rotor out of balance.
•
Inspect motor by itself with no load attached. If it
feels rough and vibrates but the bearings are
good, it may be that the rotor was improperly
balanced at the factory. Rotor must be replaced or
rebalanced.
•
Motor may have too much endplay.
•
With the motor disconnected from power turned
shaft. It should move but with some resistance. If
the shaft moves in and out too freely, this may
indicate a preload problem and the bearings may
need additional shimming.
•
Winding may be defective.
•
Test winding for shorted or open circuits. The
amps may also be high. Replace motor or have
stator rewound.
•
Bearings
continuously fail.
•
Load to motor may be excessive or
unbalanced.
•
Besides checking load, also inspect drive belt
tension to ensure it’s not too tight may be
too high. An unbalanced load will also cause
the Bearings to fail.
•
High ambient temperature.
•
If the motor is used in a high ambient, a
different type of bearing grease may be
required. You may need to consult the factory
or a bearing distributor.
•
The motor, at start
up, makes a loud
rubbing or grinding
noise.
•
Rotor may be striking stator.
•
Ensure that motor was not damaged in shipment.
Frame damage may not be repairable. If you
cannot see physical damage, inspect the motor’s
rotor and stator for strike marks. If signs of
rubbing are present, the motor should be
replaced. Sometimes simply disassembling and
reassembling motor eliminates rubbing. Endbells
are also sometimes knocked out of alignment
during transportation.
•
The motor is not coming up to speed
quickly enough.
•
Start capacitors
continuously fail.
•
Motor may not be sized properly. Verify how long
the motor takes to come up to speed. Most single
phase capacitor start motors should come up to
speed within three seconds. Otherwise the
capacitors may fail.
•
The motor is being cycled too frequently.
•
Verify duty cycle. Capacitor manufactures
recommend no more than 20, three-second starts
per hour. Install capacitor with higher voltage
rating, or add bleed resistor to the capacitor.
•
Voltage to motor is too low.
•
Verify that voltage to the motor is within 10% of
the nameplate value. If the motor is rated 208-
230V, the deviation must be calculated from 230V.
•
Starting switch may be defective,
preventing the motor from coming out of
start winding.
•
Replace switch.
•
Ambient temperature too high.
•
Run capacitor fail.
•
Verify that ambient does not exceed motor’s
nameplate value.
•
Possible power surge to motor, caused by
lightning strike or other high transient
voltage.
•
If a common problem, install surge protector.
