Nordic AH4P Series, Service Manual

Page: 18 / 30

5-Jul-2022 Page 18 002596MAN-01
FAN/BLOWER TROUBLESHOOTING
Fault Possible Cause Verification Recommended Action
Low Airflow
Dirty air filter Inspect. Replace.
Dirty air coil Inspect. Clean.
Poor ductwork Measure delta T between supply
and return ducts at the unit, and
compare to the performance tables
later in this manual. If delta T is very
high, it is an indicator of low airflow.
The constant airflow ECM blower
will provide the demand airflow
up to 0.5 inH
2
O duct backpres-
sure. The ductwork is poorly de-
signed or greatly undersized if the
fan motor cannot provide the re-
quired airflow.
Airflow called for by ther-
mostat or controller is too
low
Check control routine. Select a higher setting.
Fan operating
with wrong air-
flow (may be
hard to detect)
Fan motor’s signal har-
ness is loose
Verify that the 16-pin connector is
properly inserted into the motor.
Gently tug on each wire to verify it is
properly inserted into the connector.
Repair any loose connections.
Faulty signal harness or
faulty motor head
Ensure airflow demand
signal is present on ter-
minal strip
For non-VSP models, measure
24VAC between white/black (pin 3)
and the following at the blower mo-
tor signal harness (insert probes in
connector where wire is inserted, do
not unplug connector):
900 cfm = grey (pin 15)
1200 cfm = yellow (pin 6)
1500 cfm = yellow/black (pin14)
1900 cfm = violet (pin 2)
2300 cfm = green (pin 13)
For –VSP models, pull out the signal
plug and check for a 0-10VDC signal
between pins 3 and 10 (see wiring
diagram later in this manual).
If proper signal isn’t present, re-
place signal harness. If proper
signal is present, replace fan mo-
tor head.
Fan not operat-
ing or operating
intermittently
Fan motor’s signal har-
ness or power harness is
loose
Verify that each connector is proper-
ly inserted into the fan motor. Gen-
tly tug on each wire to verify it is
properly inserted into the connector.
Repair any loose connections.
Faulty signal harness or
faulty motor head
Ensure airflow demand
signal is present on ter-
minal strip
See above. See above.
Faulty power harness or
faulty motor
Insert the tips of the voltmeter
probes into the back of the connect-
or at the fan to measure the voltage
across the red and black wires.
Value should be 230VAC.
Replace power harness if
230VAC is not present, replace
motor if 230VAC is present.