SM Series Heat Pump
SM Series Heat Pump8733942411 (2017/07) Subject to change without prior notice
36 | Troubleshooting
UNIT TROUBLESHOOTING
Problem Mode Check Possible Cause Action
Cooling Heating
No compressor
operation but fan runs
X X No fault LED - contactor
energized
Open compressor
overload
Check for supply voltage at the load side of the
contactor. For 3 phase models check phase
rotation and voltage at all 3 phases.
Poor wiring connections Look for signs of heat on the wiring insulation.
Check that all wiring connections are secure and
properly torqued.
Burned out compressor
Does compressor hum when power
is applied?
If not check the resistance of the compressor
windings using the values shown in the
compressor characteristics chart.
Note that the compressor must be cool (70° F)
when checking the windings.
No compressor or fan
operation X
X
Power LED ON
Bad thermostat
connection / faulty
thermostat
Check thermostat and wiring. Check unit terminal
block for 24 VAC between "Y" and "C" and "G" and
"C".
Power LED OFF
Low or no supply power Ensure that the supply voltage to the unit is with
in the range shown on the unit data plate.
Faulty control transformer
Check for 24 VAC between "R" and "C" on the
unit terminal block. For 75 and 100 VA
transformers, check that the transformer circuit
breaker has not tripped. Check low voltage circuit
for overload conditions or short circuits before
replacing the transformer.
No fan operation - ECM
constant airflow motor X
XSee Action
No fan operation signal
Check for 24 VAC between "G" and "C". Check all
wiring connections.
Make sure that the thermostat connection plug is
securely connected.
Loose wiring
Check all wiring connections at motor and control
box. Check that power and control harnesses are
securely connected.
Interface board problems
Make sure that the interface board is not
damaged and that all DIP switches are in the
proper configuration (refer to the blower
performance tables).
Faulty motor
Check supply voltage to the motor.
Check that all motor wires are secure. Move the
"TEST" DIP switch to "ON" and the other switches
to
"OFF" on the "ADJUST" switch block on the
interface board - the motor
should run at 70% torque when "G" is called. With
power off spin the
motor shaft - noise, resistance or uneven motion
can be signs of motor failure.
Fan operates but motor
does not change speed -
ECM constant airflow
motor
X
X
Is motor behaviour only
observed during start-up?
Ramp-up programming
delays are still in effect
Wait for at least 5 min after the start-up and then
change the fan operation based on thermostat
call
ECM board settings
ECM board is in test mode Change the air flow setting dip switch on ECM
board per air flow table provided in installation
manual
Airflow speed tab on ECM
board is incorrect
Change the air flow setting dip switch on ECM
board per air flow table provided in installation
manual
Is motor not stopping
when no call for cooling
or heating from
thermostat
Thermostat is in
continuous fan mode Change the thermostat setting to on/off fan
operation instead of continuos fan operation
High external static
Dirty air filter, closed
dampers, grills, dirty air
coil
Remove the air filter and check that all of the
dampers, registers, and grills are open and free
flowing. If removing the filter corrects the
problem, clean or replace with a less restrictive
filter. Also check and clean as needed the blower
wheel, secondary heat exchanger (if applicable)
and evaporator coil (if applicable).
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