SERVICING
35
S-16C CHECKING ECM MOTOR WINDINGS
1. Disconnect the 5-pin and the 16-pin connectors from the
ECM power head.
2. Remove the 2 screws securing the ECM power head and
separate it from the motor.
3. Disconnect the 3-pin motor connector from the power head
and lay it aside.
4. Using an ohmmeter, check the motor windings for continu-
ity to ground (pins to motor shell). If the ohmmeter indi-
cates continuity to ground, the motor is defective and must
be replaced.
DO
DON'T
- Check-out motor, controls, wiring,
and connections before replacing motor.
- Automatically assume the motor is bad.
- Orient connectors down to prevent water
infiltration.
- Locate connectors above 7 and 4 o'clock
positions.
- Install "drip loops".
- Use authorized motor and control model #'s
for replacement.
- Replace one motor or control model # with
another (unless an authorized replacement).
- Keep static pressure to a minimum:
- Use high pressure drop filters - some have
1/2" H2O drop!
- Recommend high efficiency, low static
filters.
- Use restricted returns.
- Recommend keeping filters clean.
- Design ductwork for min. static, max
comfort.
- Look for and recommend ductwork
improvement, where necessary, in
replacement.
- Size the equipment wisely.
- Oversize system then compensate with low
airflow.
- Check orientation before inserting motor
connectors.
- Plug in power connector backwards.
- Force plugs.
ECM VARIABLE SPEED CIRCULATOR BLOWER MOTORS
5. Using an ohmmeter, check the windings for continuity (pin
to pin). If no continuity is indicated, the thermal limit (over
load) device may be open. Allow motor to cool and retest.
Motor
Connector
(3-pin)
Motor OK when
R > 100k ohm
(3-pin)
WINDING TEST