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36 | Troubleshooting
Problem
Mode
Cooling
No compressor
X
operation but fan runs
No compressor or fan
operation
X
No fan operation - ECM
constant airflow motor
X
Fan operates but motor
does not change speed -
ECM constant airflow
motor
X
8733942411 (2017/07)
UNIT TROUBLESHOOTING
Check
Heating
X
No fault LED - contactor
energized
Power LED ON
X
Power LED OFF
X
See Action
Is motor behaviour only
observed during start-up?
ECM board settings
Is motor not stopping
when no call for cooling
X
or heating from
thermostat
High external static
Subject to change without prior notice
Possible Cause
Check for supply voltage at the load side of the
Open compressor
contactor. For 3 phase models check phase
overload
Poor wiring connections
Look for signs of heat on the wiring insulation.
Check that all wiring connections are secure and
If not check the resistance of the compressor
Burned out compressor
windings using the values shown in the
Note that the compressor must be cool (70° F)
Bad thermostat
Check thermostat and wiring. Check unit terminal
connection / faulty
block for 24 VAC between "Y" and "C" and "G" and
thermostat
Low or no supply power Ensure that the supply voltage to the unit is with
in the range shown on the unit data plate.
Check for 24 VAC between "R" and "C" on the
unit terminal block. For 75 and 100 VA
transformers, check that the transformer circuit
Faulty control transformer
breaker has not tripped. Check low voltage circuit
for overload conditions or short circuits before
Check for 24 VAC between "G" and "C". Check all
No fan operation signal
Make sure that the thermostat connection plug is
Check all wiring connections at motor and control
box. Check that power and control harnesses are
Loose wiring
Make sure that the interface board is not
Interface board problems
damaged and that all DIP switches are in the
proper configuration (refer to the blower
Check that all motor wires are secure. Move the
"TEST" DIP switch to "ON" and the other switches
Faulty motor
"OFF" on the "ADJUST" switch block on the
should run at 70% torque when "G" is called. With
motor shaft - noise, resistance or uneven motion
Ramp-up programming
Wait for at least 5 min after the start-up and then
delays are still in effect
change the fan operation based on thermostat
ECM board is in test mode Change the air flow setting dip switch on ECM
board per air flow table provided in installation
Airflow speed tab on ECM
Change the air flow setting dip switch on ECM
board is incorrect
board per air flow table provided in installation
Thermostat is in
continuous fan mode
Change the thermostat setting to on/off fan
operation instead of continuos fan operation
Remove the air filter and check that all of the
dampers, registers, and grills are open and free
Dirty air filter, closed
flowing. If removing the filter corrects the
dampers, grills, dirty air
problem, clean or replace with a less restrictive
coil
filter. Also check and clean as needed the blower
wheel, secondary heat exchanger (if applicable)
SM Series Heat Pump
Action
rotation and voltage at all 3 phases.
properly torqued.
Does compressor hum when power
is applied?
compressor characteristics chart.
when checking the windings.
"C".
replacing the transformer.
wiring connections.
securely connected.
securely connected.
performance tables).
Check supply voltage to the motor.
to
interface board - the motor
power off spin the
can be signs of motor failure.
call
manual
manual
and evaporator coil (if applicable).
SM Series Heat Pump
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